KABUL, Nov 7, 2009 (AFP) - A search for two US soldiers missing in northwest Afghanistan continued Saturday after 25 soldiers were wounded in what one Western official said may have been a friendly-fire incident during the hunt.

Five of the wounded were American soldiers, a spokesman for NATO's International Security Assistance Force (ISAF), told AFP.

ISAF spokesman Lieutenant Colonel Todd Vician, of the US Air Force, told AFP: "We have nothing to confirm friendly fire."

"No ISAF members were killed," he said, confirming the injured ISAF soldiers were Americans.

Investigations into Friday's incident, believed to have happened in Badghis province, were ongoing and no further details were available, he said.

Local police in Badghis province said a party looking for the two missing soldiers clashed with Taliban and that alliance aircraft were called in to provide support.

While the ISAF withheld official comment on how the 25 were wounded, police said the casualties occurred when the air strike mistakenly targeted international troops.

A Western military officer who spoke on condition of anonymity said it appeared to be a "blue-on-blue incident," or friendly fire, with "a huge number of casualties."

NATO began its search operation in the barren, rugged area together with Afghan forces after the two paratroopers, from the 82nd Airborne Division, went missing on Wednesday during a routine supply mission.

Vician said investigations were ongoing.

The deputy police chief of Badghis, Abdul Jabar Saleh, said the missing men had drowned while trying to recover airdropped packages from a river and that their bodies had not yet been recovered.

He said a number of NATO and Afghan personnel had died as they came up against Taliban militants during the search on Friday and that alliance aircraft carried out air strikes.

"In the afternoon... during the search operation launched to find the two drowned American soldiers, a clash took place with Taliban. Then aircraft mistakenly bombed the Afghan and NATO defence lines," he said.

He said that two Afghan soldiers had been killed and 12 wounded, with three Afghan police also killed and one other wounded.

A Taliban spokesman said the toll was far higher than the Afghan police or NATO were reporting.

He denied reports that the bodies of the two US paratroopers had been retrieved from the river and were being held by the militant group.

"There was... a firefight between Taliban and Afghan and foreign forces in Murghab district of Badghis province. The fighting lasted for hours and was very intense, at a close distance," said the spokesman, Qari Yusuf Ahmadi.

"By the end of the day, foreign forces bombed the area where the clash was going on, and due to their own bombing, 32 foreign and 43 Afghan soldiers were killed."

The Taliban is known to exaggerate death tolls and to claim responsibility for incidents with which it has nothing to do.

There are more than 100,000 troops under NATO and US command deployed to Afghanistan to fight a Taliban insurgency that is now at its deadliest in the eight years since US-led troops toppled the Islamist regime in Kabul.

US President Barack Obama is currently considering a request from his military commanders to boost troop numbers by up to 40,000, a decision that is not likely to be made public for a number of weeks yet.

Separately, the Afghan army said a five-day operation that ended on Friday in northern Kunduz province had resulted in the deaths of 133 militants.

"Two Afghan army soldiers were killed and one was wounded," Abdul Wakeel Ehsas Afghan, army brigade commander in the province said.

He said 15 Taliban were arrested and nine surrendered during the operation.

As Taliban activity across Afghanistan intensifies, UN chief Ban Ki-moon said about 200 UN expatriate staff would be temporarily relocated outside Afghanistan in the wake of a deadly rebel attack on a guesthouse on October 28 which killed five UN workers.

"Approximately 200 will relocate to other duty stations in the region," the UN Secretary General told reporters in New York after briefing the Security Council on his recent visit to Kabul.

UN officials said another 400 expatriates were being relocated to safer sites within Afghanistan.