Kabul - One British soldier and three Afghan forces were killed in two separate blasts in volatile southern Afghanistan, while 26 Taliban militants were killed in clashes and NATO's airstrike elsewhere in the country, officials said Sunday.

In the latest series of home-made bomb attacks carried out by the Taliban, a British soldier was killed in an explosion in Sangin district of southern province of Helmand on Saturday, British Defence Ministry said in a statement on Sunday.

Saturday's death brought to 230 the total number of British soldiers killed in Afghanistan since their deployment in late 2001. Five British soldiers were killed on Wednesday when one of their Afghan police trainees opened fire on them during a visit of a checkpoint in the same province.

Three Afghan army soldiers were also killed on Saturday when their vehicle was struck by a roadside bomb blast in the same turbulent Helmand, Afghan Defence Ministry said in a statement.

Taliban militants rely heavily on use of roadside bombs as part of their campaign aimed at toppling the Western-backed Afghan government.

Seventeen Taliban militants were killed and one was arrested in southern province of Zabul in a fight with Afghan forces, which was supported by NATO's airstrikes, according to the Afghan Army.

The air and ground assaults on Taliban fighters started after the militants targeted an Afghan army outpost in Naw Bahar district of the province with artillery fires on Saturday, the statement said, adding that there were no casualties among the combined forces.

Nine other militants were killed in different clashes with Afghan security forces in south-western province of Farah on Saturday, Faqir Askar, the provincial police chief said.

Meanwhile, search operation to find two US soldiers, who went missing during a resupply mission in western province of Badghis on Wednesday, continues, Afghan and NATO officials said.

Three Afghan police and four army forces, who were taking part in the search, were killed on Friday when a NATO warplane bombed the forces, according to Afghan defence ministry. Five US soldiers and 15 additional Afghan forces were wounded.

Afghan and NATO troops said Sunday that they were probing the incident to find out if all the casualties on Friday were caused by the airstrike. Taliban attack was also reported.

Taliban militants have widened their insurgency to previously peaceful regions of the country, waging a nation-wide fight against the Afghan government and more than
100,000 international troops in the country.

Mohammad Omar, the provincial governor for northern province of Kunduz said Sunday that more than 130 Taliban fighters, including ten foreign militants, were killed in the past one week in three restive areas of the province.

Four Taliban commanders were also among those killed, he said. The operation was jointly conducted by Afghan forces, NATO-led German troops and US Special Forces, he added.

Eight years since the ouster of their regime, the Taliban insurgents are still a force to be reckoned with.

The US is mulling to send tens of thousands of additional troops to Afghanistan as requested by its ground commander to reverse the gains made by Taliban over the past four years.(dpa)