Afghan health officials carry the body of an aid worker into a hospital in Mazar-i-Sharif on June 2, 2015
Gunmen killed nine Afghan employees of a Czech aid organisation 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 organisation 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 organisation 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 organisation 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.
- Attacks on aid workers -
Employees of international aid organisations have increasingly come under attack in Afghanistan, even though the Taliban's official policy rejects attacks on humanitarian workers.
Last year 57 aid workers were killed, according to the United Nations Assistance Mission in Afghanistan (UNAMA). Since the start of this year, 26 aid workers have died, with another 17 injured and 40 abducted, UNAMA said.
"Being an aid worker in Afghanistan is an extremely risky business, which will only become more dangerous if authorities fail to ensure those responsible for these disgraceful attacks face justice," Horia Mosadiq, Afghanistan researcher at Amnesty International, said in a statement.
"Anything less will send the message that aid workers are a fair target."
Afghan President Ashraf Ghani also strongly condemned the killings of "innocent staff... whose job was just to help people in need".
The latest attack comes just weeks after 14 people -- mostly foreigners -- were killed in a Taliban attack on a guesthouse in central Kabul popular with international aid workers.
Five of them were Afghan employees of aid organisations including ActionAid and the Aga Khan Foundation.
In April the bullet-riddled bodies of five Afghan workers for Save the Children were found after they were abducted by gunmen in the strife-torn southern province of Uruzgan.
Official efforts to bring the Taliban to the negotiating table have so far borne little fruit.
The surge in attacks has taken a heavy toll on civilians, according to UNAMA. In the first four months of 2015, civilian casualties jumped 16 percent from the same period last year, it said.
Ghani's government has drawn criticism for failing to end growing insurgent attacks, which critics partly blame on political infighting and a lengthy delay in appointing a candidate for the crucial post of defence minister.
Ghani last month nominated Mohammad Masoom Stanekzai, a top official in the government body overseeing the country's peace process, for the job.
The post had been left vacant for months due to disagreements between Ghani and his chief executive and former presidential election rival, Abdullah Abdullah.