Kabul: A Nato airstrike in the western province of Badghis on Friday mistakenly hit a joint base housing coalition troops and Afghan security forces, killing four Afghan soldiers and three policemen, Afghanistan's Defence Ministry said on Saturday.

Nato said it and Afghan authorities were investigating whether an alliance airstrike during an operation Friday to rescue two missing American paratroopers had caused casualties. It said it could not confirm whether the base had been hit.

The alliance said reports indicated a total of seven Afghan security forces personnel and one Afghan civilian interpreter had been killed.

It added that five US and 15 Afghan soldiers, two policemen and an Afghan civilian interpreter had been wounded in several hours of fighting against insurgents during the search for the missing paratroopers.

Meanwhile, Afghanistan's Foreign Ministry said that the top UN official in the country overstepped his authority by giving instructions on how to rid the government of corruption and warlords.

Kai Eide, head of the UN mission in Afghanistan, joined a host of international figures, including US President Barack Obama, who have called on the Afghan government to take concrete steps to clean up the government following a presidential election that was marred by fraud.

"Over the last few days some political and diplomatic circles and propaganda agencies of certain foreign countries have intervened in Afghanistan's internal affairs by issuing instructions concerning the composition of Afghan government organs and political policy of Afghanistan," the foreign ministry statement said.

"Such instructions have violated respect for Afghanistan's national sovereignty."