Thirty-three people are still missing five days after a US air strike on an Afghan hospital, Doctors Without Borders warned Thursday, sparking fears the death toll could rise significantly.

Saturday's bombing in the disputed town of Kunduz killed 12 staff and 10 patients, prompting the medical aid agency to close the trauma centre.

The centre was seen as a lifeline in a war-battered region with scant medical care and which is one again on the frontline after a stunning Taliban operation.

"We are still in shock," Guilhem Molinie, the head of Doctors Without Borders (MSF) in Afghanistan, told reporters in Kabul.

"We lost many colleagues and at the moment it's clear that we don't want to take the risk for any of our staff."

MSF has set up a hotline in hopes of tracing the nine patients and 24 staff who are still unaccounted for.

"We cannot speculate on their whereabouts," the charity said in a statement.

It is possible, MSF added, that unidentified bodies remain in the hospital, but that cannot be confirmed amid the ongoing insecurity in the area.

The New York Times reported this week that the top US and NATO commander in Afghanistan thought US forces had broken their own rules of engagement.

And on Thursday, the commander -- General John Campbell -- made it clear publicly that any error was the fault of US forces and not of their Afghan allies.

President Barack Obama has apologised to MSF but three investigations -- by the US military, by NATO and by Afghan officials -- are underway and the general would not be drawn on their progress.

But, asked about allegations that Afghan troops had called in the US strike because wounded Taliban fighters were being treated in the hospital, Campbell said that would not be a justification.

"A hospital is a protected facility. We would not target a hospital," he told the US House of Representatives Armed Services Committee in Washington.

- Broke Geneva Conventions? -

"When the Afghans call for fire, that's not an automatic response. Every day the Afghans ask me for close air support and we just don't go fire some place," he said.

"We go through a rigorous procedure to put aerial fires on the ground -- A US process, under the US authorities.

"So we've got to figure out what happened in that case but I don't want people to think that just because the Afghans call fire that there's automatic fire anywhere they want it, that's just not the case."

MSF, which has condemned the attack as a war crime, is stressing the need for an international investigation, saying the raid contravened the Geneva Conventions.

Aid groups, the United Nations and a tide of global outrage have pressured Washington to come clean over the strike, which came after the Taliban overran Kunduz.

NATO Secretary General Jens Stoltenberg added to this clamour in Thursday after a meeting of NATO defence ministers in Brussels.

"We underlined the importance of a full and thorough and transparent investigation," he told reporters. "We need to have all the facts on the table."

The raid was carried out after the Taliban's brief but bloody capture of Kunduz, which has badly shaken confidence in the Afghan government's ability to hold the militants off despite NATO support.

MSF General Director Christopher Stokes told the news conference in Kabul that the charity was reviewing security at "all its operations in Afghanistan".

Molinie said MSF has not yet received any assurances that would give them the "confidence" to return to Kunduz.

Hungry, thirsty and war-wounded residents of the city, meanwhile, complained of the lack of essential medical support as they slowly emerged from their houses after days of pitched street battles.

burs-dc/sst

New York Times