Heavily armed militants stormed a Pakistani air force base on Thursday, sparking clashes that left 10 people dead and raised concerns about the safety of the country's nuclear arsenal.

One security official was killed and a plane damaged in the pre-dawn assault at PAF Base Minhas claimed by the Taliban as militants again proved able to penetrate a sensitive military site five years into an insurgency.

The first strike on a base in more than a year came amid speculation that Pakistan could bow to US demands for an operation against militants in their main fortress of North Waziristan, in the tribal belt on the Afghan border.

An official denied there were nuclear weapons on the heavily guarded base, but the audacious assault will raise further questions in the West about the dangers of Pakistan's atomic weapons falling into extremists' hands.

The Pakistan Air Force said nine attackers dressed in military uniforms and armed with rocket propelled-grenades and suicide vests targeted the base and adjacent Pakistan Aeronautical Complex at 2:00 am (2100 GMT Wednesday).

PAF Minhas, in the town of Kamra in Punjab province 60 kilometres (35 miles) northwest of Islamabad, has been attacked twice before.

The adjacent complex assembles Mirage and, with Chinese help, JF-17 fighter jets.

"Eight miscreants were killed inside the Minhas base boundary wall and one miscreant exploded himself outside the perimeters where he was hiding," the air force announced.

It said there had been a shootout "for more than two hours" and 10 hours after the assault began, spokesman Tariq Mahmood confirmed the base was "totally safe".

The Pakistani Taliban said planes at the base were being used to kill its fighters.

Spokesman Ehsanullah Ehsan dedicated the attack to late Al-Qaeda leader Osama bin Laden and claimed four Taliban fighters had been killed after destroying three aircraft and killing a dozen soldiers.

Witnesses said the attackers came round the back, scaling the wall and exploiting the holiest night of the Muslim fasting month of Ramadan to remain undetected as long as possible.

"Most of the male residents (from the village at the back) were in mosques for special prayers," local resident Athar Abbas told Express Television.

"I heard three or four explosions, there was heavy gunfire also," he said. "It appears that the militants arrived using a village track and climbed over the wall."

US state Department spokeswoman Victoria Nuland said the United States had no reason to doubt Pakistan's account that the Minhas base was free of nuclear weapons.

"We have confidence that the government of Pakistan is well aware of the range of potential threats to its nuclear arsenal and has secured its nuclear arsenal accordingly," Nuland told reporters.

"We do talk about these issues and support Pakistani efforts to keep them secure -- we have for quite a long, long time. And we don't have any reason to be concerned at this moment," she said.

Air force spokesman Mahmood said one security official had been killed and the base commander wounded in the shoulder during the attack. Previous Taliban assaults on Pakistani military bases have exacted far higher casualty tolls.

An air force statement late Thursday said Air Chief Marshal Tahir Rafique Butt had appointed a four-member board of inquiry headed by Air Marshal Syed Athar Hussain Bukhari.

The air chief also announced an award of one million rupees ($10,600) for the "martyred" soldier's family, it said.

In May 2011, it took 17 hours to quell an attack on an air base in Karachi claimed by the Taliban, piling embarrassment on the armed forces just three weeks after US troops killed bin Laden in Pakistan.

Pakistan has been on alert for independence day on Tuesday and the Muslim festival of Eid, which is expected to begin at the weekend.

Elsewhere in the northwest, gunmen in military uniforms pulled 20 Shiite Muslims travellers from vehicles and shot them dead in the northwestern district of Mansehra, the third such incident in six months, officials said.

On Tuesday, the head of the army, General Ashfaq Kayani, used his independence day address to describe the war on terror as "our own war and a just war" -- not the American conflict as often portrayed.

Pakistan says 35,000 of its people, including more than 3,000 soldiers, have been killed as a result of terrorism since the 9/11 attacks and the 2001 US-led invasion of neighbouring Afghanistan.

The government was forced to deny any danger of Pakistan's nuclear warheads falling into the wrong hands.

"We have a robust command and control, so nobody should really worry about the security and safety of our assets," said foreign ministry spokesman Moazzam Ahmad Khan.

The base in Kamra was most recently targeted on October 23, 2009 when a suicide bomber killed eight people.