Seven US troops were killed in two Taliban-style bomb attacks Monday in southern Afghanistan, the area hardest hit by the insurgency nearing the end of its ninth and most deadly year, NATO told AFP.

One attack killed five soldiers, NATO's International Security Assistance Force (ISAF) said in a statement.

With the latest deaths, 478 foreign soldiers, including 315 Americans, have been killed in the Afghan war so far this year, according to a tally based on that kept by the icasualties.org website. Seven US soldiers were killed in a wave of attacks at the weekend.

The war is dragging towards its 10th year since the toppling of the Taliban regime in late 2001, with almost 150,000 United States and NATO troops in the country battling to quell the insurgency.

A total of 2,046 foreign troops have died in the conflict, 1,262 of them Americans.

The Taliban leadership has said that anyone associated with the foreign forces, with foreign organisations or the government of President Hamid Karzai is a legitimate target.

Officials are regular victims, with a bomb blast in the eastern city of Jalalabad Monday killing a district chief and wounding up to five others.

"The explosion targeted the vehicle of La'al Poor district chief Sayed Mohammad Pahlawan at 9:15am this morning," said Ahmad Zia Abdulzai, spokesman for Nangahar province, of which Jalalabad is the capital.

"He was on his way to the office of the provincial governor," he told AFP.

He said the explosives had been placed in Pahlawan's car and detonated by remote control, adding that the wounded included three of his bodyguards.

The vehicle exploded just 15 metres (yards) from the governor's office, he said.

The interior ministry condemned the killing of Pahlawan as an "un-Islamic and inhumane act by insurgents". It said five other people were wounded in the blast.

Jalalabad, more than two hours drive east of Kabul, has seen a recent escalation in violent incidents as Taliban-led insurgents spread their footprint in reaction to an increased presence of foreign forces.

The insurgency is at its most intense in the southern provinces of Kandahar and Helmand, but it has rapidly spread to other regions in the past year.

NATO is struggling to turn the tide on the Taliban but officials say that the arrival of 30,000 extra troops, as part of US President Barack Obama's surge aimed at speeding an end to the war, is having an impact.

Officials in southern Zabul province, neighbouring Kandahar, said 24 insurgents, including two Taliban commanders, were captured in a joint Afghan-coalition operation Sunday while trying to cross into Pakistan.

ISAF said Monday it was investigating reports that one of its convoys had been hit in a bombing in Kandahar province. An AFP reporter at the scene on the Kandahar-Herat highway said one of the ISAF armoured vehicles was on fire.

Separately, Afghan intelligence agency the National Directorate of Security (NDS) said it had seized "a large amount of military equipment including arms and munitions" from a private security firm.

It said the materiel was "being illegally transferred by a private security company from Kabul city to the airport and then to unknown destination".

The NDS statement named the security firm as Blue Hackle, a member of the British Association of Private Security Companies.

"The weapons were provided to this company by arm smugglers," it said, adding that they had been confiscated amid an investigation.

President Karzai has ordered that all 52 private security companies operating in the country disband by the end of the year, sparking fears of a security crisis as they are contracted by most foreign entities and the military.