Syrian President Bashar al-Assad could take "credit" for swiftly moving to eliminate his regime's chemical arms, top US diplomat John Kerry said Monday, after UN experts began destroying Syria's missile warheads and aerial bombs.

The operation, performed by Syrian personnel under the supervision of international disarmament experts, took place under the terms of a UN Security Council resolution that will see Damascus relinquish the banned arms.

"The process has begun in record time and we are appreciative for the Russian cooperation and obviously for the Syrian compliance," Kerry told reporters alongside Russian Foreign Minister Sergei Lavrov after talks in Indonesia.

"I think it's extremely significant that yesterday, Sunday, within a week of the (UN) resolution being passed, some chemical weapons were being destroyed," the US Secretary of State said.

"I think it's a credit to the Assad regime, frankly. It's a good beginning and we welcome a good beginning."

Syria agreed to give up its chemical arsenal under last month's UN resolution that enshrined an agreement struck between Washington and Moscow aimed at averting US military action.

Under the plan, Syria's chemical weapons mixing and production facilities must be destroyed by November 1.

On Sunday, a statement released by the United Nations and the Organisation for the Prohibition of Chemical Weapons (OPCW) said workers "used cutting torches and angle grinders to destroy or disable a range of items".

The Syrian workers were destroying or disabling a "range of items", including "missile warheads, aerial bombs and mixing and filling equipment", the statement added.

The team faces the daunting task of disposing of an estimated 1,000 tonnes of the nerve agent sarin, mustard gas and other banned arms at dozens of sites in Syria by mid-2014.

International disarmament experts, who arrived on Tuesday, were also "monitoring, verifying and reporting" whether Assad's government provided accurate information on its chemical stockpiles.

As the operation got under way, Assad admitted in an interview that his government had made "mistakes" in the country's brutal conflict.

But he again denied that his forces used chemical weapons in an August 21 attack that killed hundreds of civilians.

The assault led to threats of a US strike and eventually the UN resolution requiring Syria to turn over its arsenal.

In Damascus, meanwhile, a barrage of mortar rounds slammed into a Christian neighbourhood, killing eight people.

And UN-Arab League envoy Lakhdar Brahimi called on Assad's regime and the rebels to hold peace talks "without preconditions".

The OPCW has said other methods to render Syria's production facilities unusable could include explosives, sledgehammers or pouring concrete.

UN leader Ban Ki-moon is expected to send a report to the Security Council on Monday setting out in more detail the logistics of what is considered one of the biggest and most dangerous disarmament operations ever staged because the Syria war is still raging.

Assad says 'mistakes happen'

Assad insisted his government was being "very transparent" with the UN-OPCW team.

"The experts can go to every site. They are going to get all the data from us, they will verify them, and then they can make a judgement about our credibility," he told Germany's Spiegel magazine.

But he also acknowledged that mistakes had been made in responding to the uprising that took the form of peaceful protests when it began in March 2011 before escalating into a civil war after a brutal crackdown by government forces.

More than 115,000 people have since been killed, activists say. Two million people have become refugees and millions more have been displaced inside Syria.

"Whenever political decisions are made, mistakes happen," Assad said.

"We all make mistakes. Even a president makes mistakes."

Although acknowledging that "reality is not black and white", he insisted that "our fundamental decisions were right".

"You can't just absolutely say 'they carry 100 percent of the blame and we carry zero'," Assad said.

"But basically it's correct that we are defending ourselves."

The president also lashed out at US accusations that he had killed his own people with chemical weapons, saying President Barack Obama "presents not a single piece of evidence. Not a shred of evidence.

"He has nothing to offer but lies," he added.

The magazine reported that German intelligence services believe Iran has allowed Assad's regime to station warplanes on its territory as protection from foreign attack.

State news agency SANA said eight people were killed and 27 wounded in the Damascus district of Qassaa when four mortar rounds slammed into the Christian neighbourhood.

Rebels regularly fire into Damascus from rear bases in neighbourhoods around the city.

Despite the fighting, UN-Arab League peace envoy Brahimi told France's TV5 Monde that he hoped the two sides would agree to attend a peace conference in Geneva in mid-November "without preconditions".

"We are going to Geneva without preconditions," Brahimi said.

"Mr Bashar al-Assad cannot say that he does not want to negotiate with 'X' or 'Y' and it's the same thing for the opposition."

Syria's chemical weapons arsenal
Beirut (AFP) Oct 06, 2013 - International disarmament experts began the mammoth task of destroying Syria's chemical arsenal on Sunday under a hard-won deal that averted threatened US military action following an August 21 gas attack.

The team from the Organisation for the Prohibition of Chemical Weapons (OPCW) arrived in Syria on October 1 to launch its mission to destroy the decades-old arsenal under the terms of a landmark UN Security Council resolution passed unanimously on September 28.

The task is huge, as Syria's arsenal is believed to include more than 1,000 tonnes of sarin, mustard gas and other banned chemicals stored at an estimated 45 sites across the war-torn country.

The mission is the first in OPCW history to take place in a country wracked by civil war.

President Bashar al-Assad's regime is accused of using chemical weapons in attacks on two rebel-held areas near Damascus that US intelligence and the Syrian opposition charge killed hundreds of people.

On September 1, US Secretary of State John Kerry said Washington had clear intelligence proving sarin gas was used in the August 21 assault by regime forces.

A French intelligence report released on September 2 said there was "massive use of chemical agents" on the day of the attacks in Syria and that only the regime could have been responsible.

The report said Syria "had one of the biggest operational stocks of chemical weapons," including an arsenal of more than 1,000 tonnes comprising sarin and mustard gas and more powerful neurotoxic agents.

It also said Syrian scientists were working on more lethal nerve agents.

The Syrian regime acknowledged for the first time on July 23, 2012, that it had chemical weapons and threatened to use them in case of a Western military intervention, but never against the Syrian population.

One of the few countries not to have signed the Chemical Weapons Convention until last month, Syria began its chemical weapons programme in the 1970s with the help of Egypt and the then Soviet Union.

In March this year, the government and the rebel forces battling to topple it accused each other of using chemical weapons in the more than two-year conflict.

Britain, France and the United States have accused Syrian forces of using chemical weapons against insurgents on several occasions.

Russia, a key ally of Syria along with Iran, has said it has proof sarin gas was used by the rebels.

In the 1990s, Moscow provided Syria with support for the programme, followed by Tehran since 2005, according to the Nuclear Threat Initiative (NTI), an independent organisation tracking data on weapons of mass destruction.

An analyst at the non-proliferation and disarmament programme of the International Institute for Strategic Studies (IISS) says Syria has the biggest chemical weapons programme in the Middle East, launched with the goal of counterbalancing Israel's nuclear programme.

On September 26, the Washington Post reported that a confidential Russian-US assessment of Syria's chemical arsenal revealed that much of it was unweaponised, making it easier to destroy.

On January 30, Israeli warplanes bombed a ground-to-air missile battery and adjacent military complex near Damascus suspected of holding chemical weapons, with Israel saying it feared their transfer to Lebanon's Shiite militant group Hezbollah, according to a US official.

According to The New York Times, the raid could have damaged Syria's main research centre into biological and chemical weapons.