The international operation to destroy Syrian chemical weapons entered its final phase on Wednesday, with the stockpile loaded onto a US military ship equipped to dispose of them.

Hundreds of tonnes of mustard gas and ingredients to make Sarin nerve gas were transferred from a Danish freighter in the southern Italian port of Gioia Tauro amid tight security.

"Italy has proven its capacity for great efficiency in this delicate operation of international security," Environment Minister Gian Luca Galleti said as he declared the transfer finished.

Workers cracked out the champagne to celebrate the end of an intense and quick-paced operation, according to Italian news agency ANSA.

Ahmet Uzumcu , director general of the Organisation for the Prohibition of Chemical Weapons (OPCW), which oversaw the operation, said it had gone "without incidents" and thanked "Italy for having offered the Gioia Tauro port", praising "all the staff involved."

With the chemical agents safely transferred, both ships were due to set sail immediately, with the US Cape Ray taking its new cargo to be destroyed in international waters.

An exclusion zone had been set up around the port in the Reggio Calabria region for the transfer, and the containers were moved from one ship to the other by crane and a vast climbing platform.

- 'The poison ship' -

Safety officers in the area monitored for the possible release of dangerous toxins into the air amid protests by Italian environmentalists.

The disposal process marks the culmination of a programme to rid Syria of its chemical weapons stockpile after the outcry that followed chemical attacks by the Assad regime in the suburbs of Damascus on August 23 last year, that may have killed as many as 1,400 people.

The transfer and disposal of the weapons and materials "could open up new possibilities for disarmament and non-proliferation in the region," Italian Foreign Minister Federica Mogherini said.

But despite government assurances that the port was used to handling highly dangerous toxic substances, the procedure sparked concern in Italy.

Dozens of protesters had gathered in the nearby town of San Ferdinando on Tuesday, worried by the risks to health involved in allowing the Danish freighter Ark Futura, which they dubbed "the poison ship", to dock.

The protest group SOS Mediterraneo said destroying the weapons at sea risked having a devastating effect on Italy's pristine beaches and seaside communities, with a spokesman saying "securing such dangerous agents should be done on land, in absolutely secure conditions."

- High security -

Angelo Bonelli, leader of Italy's Green Party, also asked the government "for immediate assurances" that "residual toxins produced" during the destruction of the agents will not pollute the waters or impact the fishing industry.

The port had stepped up security for the transfer, sealing off access roads and barring entry to any non-authorised people.

Once the MV Cape Ray moves back out into international waters, the process to destroy the materials is expected to take between 45 and 90 days.

The US vessel has been equipped with two Field Deployable Hydrolysis Systems -- portable treatment plants capable of "neutralising" the most dangerous Syrian chemical agents.

The process should destroy more than 99 percent of the chemicals, reducing the lethal agents into a sludge similar to low-level hazardous industrial waste, which will then be disposed of by private waste treatment facilities.

Syria shipped out its stockpile of chemical weapons under the terms of a UN-backed and US-Russia brokered agreement to head off Western air strikes against the regime last year.

Transfer of Syrian chemical weapons complete: Pentagon
Washington (AFP) July 03, 2014 - The transfer of Syrian chemical weapons from a Danish container ship to a US vessel was completed on Wednesday in an Italian port, the Pentagon said in a statement.

The disposal process marks the culmination of a program to rid Syria of its chemical weapons stockpile after the outcry that followed chemical attacks by the Bashar al-Assad regime in the suburbs of Damascus on August 23 last year, that may have killed as many as 1,400 people.

"The transfer of Syrian chemicals from the Danish container ship Ark Futura to the Motor Vessel Cape Ray is complete," said Pentagon press secretary Rear Admiral John Kirby.

"Cape Ray departed the Italian port of Gioia Tauro this afternoon for international waters in the Mediterranean Sea, where neutralization operations will soon begin.

"The neutralization process should take several weeks to complete."

Hundreds of tonnes of mustard gas and ingredients to make Sarin nerve gas were transferred from the Danish vessel in the southern Italian port amid tight security.

"Secretary Hagel is grateful to Danish and Italian authorities for their support in this process and is enormously proud of everyone who helped make possible this safe and incident-free transfer," Kirby said.

"He extends a special thanks to the men and women of the Cape Ray, Naval Forces Europe, and US European Command teams for their impeccable planning and execution."