The leader of the Lebanese militant group Hezbollah has accused Israel of being behind the 2005 assassination of former Lebanese PM Rafik Hariri.

In a fiery speech, Sheikh Hassan Nasrallah said he would prove the claim at a press conference next week.

The BBC's Jon Leyne says Mr Nasrallah is trying to pre-empt a UN report due to implicate Hezbollah in the killing.

Mr Nasrallah was speaking hours after a firefight on the Lebanon-Israeli border left five people dead.

Referring to the rare exchange of fire, he said his forces were ready to join the fighting.

Mr Hariri and 22 other people were killed in Beirut in a car bomb in 2005.