The Taliban's intensified campaign against the government and foreign troops supporting it this year has spawned the worst violence since the hardline Islamists were ousted after the September 11 attacks in 2001.

The suicide blast went off as foreign troops were passing through Lashkar Gah, capital of Helmand province, an official said.

Nato troops were in the area at the time but none was hurt, an alliance spokesman said.

Near Kabul, a roadside bomb killed an Italian Nato soldier and seriously wounded two compatriots.

The Taliban claimed both blasts.

Two years ago, suicide attacks were rare in Afghanistan, but this year there have been dozens of such attacks aimed at the government and foreign forces.

Among the dead in the Helmand blast were six policemen and soldiers. The rest were civilians, many queuing to do paperwork for a pilgrimage to Mecca, officials said.

"It was a suicide attack on a road in front of the governor's office," police official Mohammad Ayoub said in Lashkar Gah.

Taliban spokesman Qari Mohammad Yousuf claimed responsibility saying the bomber was from Helmand. A suicide blast in a market in the same town killed 17 people on August 28.

Another Taliban spokesman claimed responsibility for the blast just south of Kabul that targetted an armoured personnel carrier. Nato said five soldiers were wounded.

The violence this year has raised concerns for the country, a central battlefield in the war on terrorism. Optimism that followed successful elections in 2004 and 2005 has evaporated.

The United States, which had been hoping to trim its Afghan force, has about 20,000 troops in the country. Nato, waging its biggest ground operation, has a similar number and is seeking more.

Twenty Taliban were killed in a clash in the southern province of Uruzgan on Monday, Nato said. In Paktika province on the Pakistani border, a suicide bomber's explosives went off accidentally, killing him and six accomplices, an official said.

The Taliban have surged in strength because of links with the booming drugs trade and the support of militant networks in Pakistan. They are also capitalising on anger over poverty and corruption, analysts say.

While more active, the Taliban have suffered heavy casualties. Well over 2,000 have been killed this year, according to figures from Nato, the U.S. military and the government. The Taliban reject the figures.

Nearly 140 foreign troops have been killed in fighting or accidents during operations since January.