A roadside attack killed three coalition soldiers and an Afghan contractor, while two Afghan security forces and 31 Taliban militants were killed in separate incidents in Afghanistan, officials said Tuesday.

The three soldiers and the local contractor were killed in a roadside bomb blast in eastern Afghanistan on Tuesday, the US military said in a statement.

The statement did not reveal the nationalities of the deceased soldiers nor did it provide the exact location for the incident.

But an Afghan police official, who did not want to be named, said that the incident took place in Nejrab district of the north-eastern province Kapisa as the troops were patrolling in the area.

He said the dead soldiers belonged to the US military forces.

Meanwhile, NATO aircraft targeted a group of Taliban militants who were surrounded by Afghan police forces in southern Afghanistan, killing 15 militants, police said.

The aerial bombing took place Monday night after local police forces, acting on intelligence information, surrounded a garden in Sozak village outside Tarin Kot, the provincial capital of Uruzgan province, Juma Gul Hemat said.

"We had intelligence information that the Taliban had gathered in the garden to plan their terrorist attacks in the province," Hemat said, adding that once the area was pinpointed, NATO aircraft were called in to bomb the militants.

"Fifteen bodies of the militants, who along with their weapons had been badly torn to pieces, were recovered by the police," the police chief said.

He said no civilians were killed or hurt in the air raid, which was conducted far from houses.

Hemat added that there were unconfirmed reports that Mullah Janan Agha, a rebel operational commander in the province, was present in the meeting but said he could not confirm if Agha was also killed in the raid.

Twelve other militants were killed in Zadran district of south-eastern Paktia province on Monday after a group of Taliban militants attacked the district centre, Rohullah Samoon, spokesman for the provincial governor, said.

Samoon said nine of the insurgents were Chechens and the others were Afghan and Pakistanis.

NATO-led forces also confirmed the incident and said that 20 insurgents attacked the district centre with light weapons and rocket-propelled grenades.

"The combined force, including air support, killed most of the insurgents," the alliance statement said, adding that no Afghan or NATO forces were killed or wounded in the battle.

Four insurgents and one Afghan policeman were killed in a separate firefight in Jalriz district of the south-western province Wardak early Tuesday, government spokesman Adam Khan Sirat said.

He said two other Taliban were wounded in the clash that ensued after militants ambushed a police vehicle in the area.

An Afghan army soldier was, killed and two others were wounded when bomb fixed on a bicycle was detonated by a remote control in southern Kandahar city on Tuesday, Defence Ministry spokesman General Zahir Azimi said.

Because of the remoteness of the area, it was difficult to verify officials' claims of Taliban casualties independently.

About 4,000 people - mostly insurgents - have been killed in the Afghan conflict so far this year, according to figures provided by Afghan and international military sources.