Afghan suicide attack kills 21 Afghans, two Brits - AFP

A suicide bomber blew himself up in southern Afghanistan, killing 21 Afghan civilians and two British soldiers in one of the deadliest such attacks in months, officials said Friday.

The attack on Thursday tore through a busy bazaar in Helmand province, a Taliban stronghold where British soldiers have had control of several provinces and foreign troops have faced some of their toughest fighting.

Afghan authorities said Thursday a dozen Afghan civilians were killed. On Friday, they said this toll had risen as people died of their injuries.

"Twenty-one people are dead and 22 wounded," Helmand government spokesman Daud Ahmadi told AFP.

All the dead were civilians and some were children, but it was not yet established how many, he said. Two policemen were among the wounded.

The NATO-led International Security Assistance Force said two of its troops died in the blast but did not give their nationalities -- later confirmed by the British defence ministry.

It took to 100 the number of foreign soldiers to lose their lives in Afghanistan this year, most of them in attacks, according to a toll by the icasualties.org website the tracks the wars in here and in Iraq.

There was no claim of responsibility for the blast, which was carried out by an attacker on a motorcycle packed with explosives.

Shop owner Feda Mohammad said Afghan and British forces were on patrol in the area, some walking and others following in tanks.

"A suicide bomber on motorcycle headed from a street to the main road where forces were patrolling and then he fell to the ground. People gathered to help him up. When the ISAF troops arrived, he detonated himself," he said.

It was similar to scores of other attacks carried out by Taliban insurgents, who are particularly active in Helmand where they are tied into the lucrative production of opium and heroin.

Thursday's bombing was the deadliest such attack since a suicide bomber wearing police uniform killed 25 policemen in the southern province of Uruzgan in February, authorities said. The Taliban claimed responsibility.

There are about 70,000 foreign troops stationed in Afghanistan to help the Western-backed government counter the insurgents, who are deemed an international threat. About 8,300 of those foreign soldiers are British.

The Taliban were in power from 1996 until the 2001 US-led invasion to oust the hardline Islamist movement in the wake of the September 11, 2001 attacks on the United States.

The rebels warned last week that they would step up attacks on government officials and troops.

Four British soldiers were killed in attacks in Helmand on Thursday, the defence ministry said.

The latest fatalities brought to 157 the number of British troops killed in Afghanistan since the 2001 US-led invasion in which Britain played a part.