A large group of Taliban attacked the headquarters of Nawzad district in the southern province of Helmand on Wednesday, sparking hours of fighting in which US-led coalition warplanes were called in, provincial spokesman Muhaidin Khan said.

A spokesman for the British military deployed in Helmand confirmed the clash. There were claims of civilian casualties but the coalition said these could not be confirmed.

In another battle in the province on Wednesday, the coalition said it had killed a Taliban commander in the Musa Qala district after about 20 fighters attacked a patrol near a village.

Meanwhile, police in Kabul said they arrested a man planting a bomb near the information ministry on Thursday just a week after a series of small bomb blasts struck the capital.

The Taliban claimed responsibility for the blasts. But intelligence sources said a host of disaffected groups could have been responsible.

In other violence, a bomb fixed to a bicycle exploded near a  shrine in the normally peaceful northern Shia city of Mazar-i-Sharif on Thursday, wounding up to five people, police said.