KABUL, Afghanistan - A roadside bomb in eastern Afghanistan killed four American troops Sunday, as bombings and clashes elsewhere in the country killed 14 other people, officials said.

A U.S. statement indicated the troops were based in Jalalabad.

The Taliban regularly use roadside bombs against Afghan and foreign troops. Last year the number of such attacks rose by 30 per cent, according to NATO figures.

Thousands of new American troops are joining the fight in Afghanistan this year, trying to reverse Taliban gains and help extend the governance in remote parts of the country.

The centre of the Taliban insurgency is in southern Afghanistan, where a roadside bomb hit a convoy carrying the mayor of Kandahar city on Sunday, killing a civilian and wounding two others, said Najibullah Khan, a police spokesman. The mayor survived the blast.

Separately, a suicide bomber on foot in the capital of Kabul killed two Afghan civilians, said Lt.-Gen. Abdul Rahman Rahman, Kabul's police chief.

The bomber -- who had been targeting a NATO patrol -- also wounded 14 other civilians, the Interior Ministry said in a statement. No foreign troops were wounded or killed, the statement said.

In Kandahar's Maywand district, the U.S. coalition and Afghan special forces conducting a raid in Kandahar's Maywand district -- aimed at a network supporting foreign fighters in the area -- killed five militants "who manoeuvred on the force ... during the operation," a U.S. military statement said.

On Saturday, a French soldier and five Afghan troops were killed during a clash with militants in Kapisa province, officials said Sunday.

Cmdr. Christophe Prazuck, spokesman for France's Defence Ministry, said the operation involved air support from Predator drones and other allied aircraft, and that dozens of militants "were hit hard." He didn't provide casualty estimates.

France has 3,300 troops fighting in NATO- and U.S.-led military operations in Afghanistan.

Rahmatullah Safi, Kapisa's deputy governor, said five Afghan soldiers were also killed in the operation.