Anti-government protesters in Libya's capital Tripoli have reportedly come under heavy gunfire after Friday prayers.

One eyewitness described the scene as a massacre with the sky ''raining bullets''.

As the US announced it will impose sanctions against Libya, its leader, Colonel Gaddafi, called on his supporters to defend the nation.

His son also went on television to say that he and his father would never leave Libya alive.

The BBC's Jeremy Bowen has been invited to Tripoli by the Libyan authorities.