Two Afghan police officers were killed in a clash with foreign troops conducting a night raid southwest of the Afghan capital, Kabul, early on Saturday, police and military officials said, adding to Afghan pressure to stop the raids.

Night raids, which foreign troops say are one of their most effective weapons in the fight against insurgents, are a major cause of friction between President Hamid Karzai and his Western backers. Karzai has said repeatedly he wants them stopped.

Saturday's incident happened when the soldiers, who were involved in a night raid which had not been coordinated with the police, ignored orders to halt when spotted by officers in Ghazni province, said Ghazni police chief Zorawar Zahid.

Shots were fired in the resulting clash, he said.

Foreign troops were planning to conduct night raids but a firefight took place when they failed (to obey) police orders to stop, Zahid said.

The NATO-led International Security Assistance Force (ISAF) said a combined coalition and Afghan force called in air support after being fired on at a checkpoint by rocket-propelled grenades, mortar bombs and guns.

After multiple attempts to identify themselves as friendly forces, the security force was unable to stop the threat and engaged the checkpoint in self-defence, killing two individuals, ISAF said in a statement.

Afghanistan wants the United States and NATO to agree to stop carrying out night raids on Afghan homes as a precondition to signing a long-term alliance with Washington, Karzai said at a meeting of Afghan political and community leaders on Wednesday.

That meeting, at which the future of Afghanistan's relationship with America is under discussion, is due to finish on Saturday.

Parts of Ghazni province are expected to be included in the next phase of a security handover to Afghan forces under a plan agreed by the coalition and for foreign combat troops to leave Afghanistan by the end of 2014.

(Additional reporting by Hamid Shalizi; Writing by Jan Harvey; Editing by Daniel Magnowski and Paul Tait)