KABUL, Aug. 29 (Xinhua) -- The U.S.-led coalition forces killed 18 extremists and two explosions claimed four lives in the insurgent southern Afghanistan, the military and an Afghan official said Tuesday.

    About 60 enemy fighters ambushed coalition troops on Monday in Cahar Cineh district with small arms, machine gun and rocket propelled grenades, coalition forces said in a statement.

    After the initial reaction to the ambush killed three extremists, coalition forces employed joint fire, killing 15 additional enemy, it added.

    Three other enemy fighters were detained for questioning, it said, adding no injuries to coalition forces were reported.

    "Coalition forces, in support of NATO-ISAF objectives, will continue with counterterrorist operations in southern Afghanistan," said Maj. Luke Knittig, spokesman for the NATO-led International Security Assistance Force (ISAF).

    Most of the 20,000 coalition troops are deployed in eastern Afghanistan to hunt down militants there, while a small group of coalition forces still stay in Uruzgan to fight insurgents.

    About 21,000 ISAF troops are taking charge of security in other parts of the volatile country except the eastern region.

    On Tuesday, two blasts killed four persons including two policemen in southern Afghanistan.

    A mine planted by insurgents struck a police vehicle in the Greshk district of Helmand province at 9:00 a.m. local time, killing two policemen, Hajji Mohiudin Khan, spokesman of the provincial government, told Xinhua.

    Meantime, Noor Mohammad Paktin, police chief of the neighboring Zabul province, said militants ambushed a vehicle in the Shahjoi district of the province on Tuesday morning, wounding four people, all of whom were guests of the provincial governor.

    On the same morning, a roadside bomb, targeting an ISAF convoy, killed two Afghan civilians and injured another on a highway south of Kandahar city, capital of Kandahar province, ISAF said in a statement.

    There were no ISAF casualties in the attack, it added.

    Southern Afghanistan has been a hotbed of Taliban and other antigovernment militants, who attack government and foreign troops frequently.

    Afghanistan is suffering from a rise of Taliban-linked violence this year, during which over 1,900 people, mostly Taliban rebels, have been killed. Enditem