Taliban bombers killed five Polish soldiers in an attack on their convoy in Afghanistan on Wednesday, the deadliest single loss for Warsaw's NATO contingent in the 10-year war.

"This is the most deadly attack in the history of Polish military missions abroad," Poland's Prime Minister Donald Tusk said in comments broadcast in Poland Wednesday.

The five soldiers were killed by what Tusk described as a "very powerful explosive device" while on patrol. The attack took place on a "road considered to be safe until now," he added.

Poland has 2,600 soldiers in Afghanistan and is one of the largest contributors to NATO's US-led International Security Assistance Force (ISAF), which expects to withdraw all combat troops by the end of 2014.

In Kabul, ISAF confirmed that five NATO soldiers were killed in an attack in the southeastern province of Ghazni, where Polish troops are responsible for security, but declined to release their nationalities in keeping with policy.

Ghazni provincial police chief Dilawar Zahid said the attack took place in the Rawza area of Ghazni city at 11:30 am (0700 GMT).

He confirmed casualties, but could not give an exact number.

A witness told AFP that an ISAF vehicle had been "totally destroyed" and saw helicopters evacuating casualties.

The Taliban claimed responsibility in a text message spokesman Zabihullah Mujahid sent to AFP. He claimed the Taliban had targeted a Polish convoy and killed several NATO soldiers, without providing any evidence.

The hardline Islamist militia, which ruled Afghanistan from 1996 until the 2001 US-led invasion, is waging a 10-year insurgency to evict Western troops and return to power.

Wednesday's killings bring to 36 Poland's death toll from the conflict in Afghanistan, where 140,000 US-led foreign troops are fighting a decade-long Taliban insurgency and supporting Afghan President Hamid Karzai's government.

It was the deadliest single incident for Polish troops in Afghanistan.

Poland first sent forces to Afghanistan in March 2002, shortly after the Taliban regime collapsed following the 2001 US-led invasion.

Western capitals have started to withdraw combat troops from Afghanistan as part of plans to transfer increasing responsibility for security to Afghans.

But thousands of foreign soldiers are expected to remain in the war-torn country in a training and mentoring capacity well after 2014.

In the east on Wednesday, police also shot dead a would-be suicide bomber before he could detonate his explosives at a bank, officials said.

Officers are hunting a second attacker who also tried to target a branch of the Kabul Bank in Khost city.

"One guard was wounded in the incident," the interior ministry said.

"A suicide bomber was shot dead by police before reaching his target in front of the Kabul Bank branch in Khost city," Khost provincial police spokesman Zirat Gul Mangal said.

Khost, which borders Pakistan, is a stronghold of the Haqqani network, a faction of the Afghan Taliban loyal to Al-Qaeda and blamed by the Americans for some of the most-high profile attacks in Afghanistan.

In February, a gun and suicide attack on a branch of the Kabul Bank left 38 people dead in Jalalabad, which is also near the Pakistani border.

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