Gunmen killed nine Afghan employees of a Czech aid organization in their beds during an overnight raid in northern Afghanistan Tuesday, one of the deadliest recent attacks on humanitarian workers in the war-battered country.

Gunmen killed nine Afghan employees of a Czech aid organization in their beds during an overnight raid in northern Afghanistan Tuesday, one of the deadliest recent attacks on humanitarian workers in the war-battered country.

No group has so far claimed responsibility for the killings in the relatively tranquil Balkh province, but the Taliban are intensifying their annual spring offensive despite repeated government attempts to reopen peace talks.

The nine victims were shot as they slept in a guesthouse belonging to People in Need (PIN), a Czech organization that has been active in Afghanistan since 2001, delivering aid to remote communities in the east and north.

"Those killed in Zari district of Balkh province include two drivers, two guards and five project staff, which included a woman," PIN country director Ross Hollister told AFP.

"They were killed in their beds while they were sleeping," he added.

Hollister said the organization has been working in that area since 2002 and had no forewarning of the raid.

Tuesday's attack is among the worst ever on aid workers in Afghanistan, who have increasingly been casualties of a surge in militant violence in recent years.

PIN condemned the attack, saying in a separate statement that it was "unprecedented in its brutality" and had prompted the organization immediately to suspend all work in Afghanistan.

"Investigation is ongoing, the identity of the attackers is not known, but according to available information they did not originate from the area," the statement said.

Abdul Razaq Qaderi, the deputy police chief of Balkh, said police had launched a search for the gunmen.