Four US soldiers, serving in Nato's International Security Assistance Force, were killed when a bomb blew up their vehicle as they drove over a bridge in the northern province of Kunduz, international and Afghan officials said.

'I can confirm that four ISAF soldiers were killed,' an ISAF officer said on condition of anonymity. They died 'due to an improvised bomb explosion in northern Afghanistan'.

He would not comment on their nationalities but Afghan officials and the defence ministry of Germany, which is in charge of ISAF in the north, said they were US nationals.

'We have learnt today that four US soldiers were killed in the Kunduz region by an IED (improvised explosive device),' ministry spokesman Thomas Raabe told a press conference in Berlin.

Kunduz police chief Abdul Razaq Yaqoubi said two elderly Afghan men who were passing by were also killed and two children were wounded.

A spokesman for the Taleban, Zabihullah Mujahed, said his militia was responsible. The radical Islamist Hezb-i-Islami faction is also active in Kunduz, which has recently seen a spike in attacks by insurgents.

ISAF announced separately that another two of its soldiers were killed by a bomb in southern Afghanistan, but it gave no further details, including their nationalities.

However, the attack was not in Helmand province where thousands of US and British troops have moved into insurgent strongholds in the past weeks, a spokesman said.

Another ISAF soldier 'died of injuries sustained as a result of an insurgent attack' in eastern Afghanistan, ISAF said separately, giving no details.

Early Monday, a suicide attacker blew up an explosives-filled minivan outside a massive ISAF base outside the southern city of Kandahar.

It killed two Afghan truck drivers and wounded 11 other Afghans, including two soldiers, army corps commander General Shair Mohammad Zazai told reporters. -- AFP