A senior Taleban official in Afghanistan has said two Pakistani nationals are still being investigated for the killing of a UN official in August, which led to the withrawal of United Nations aid workers.

The official, Qari Deen Mohammed, said the suspects had denied the charges and the inquiry was proceeding slowly.

The UN has called for more progress in the investigation.

The Italian UN official, Colonel Carmine Calo was shot dead hours after American air strikes on targets in Afghanistan.