Two Turkish policemen have been killed and four other people injured after unknown assailants opened fire near the US consulate in Istanbul, CNN Turk says.

TV images showed four bodies on the ground in front of the consulate.

Though initial reports said that only one gunman had opened fire, later reports suggested that more than one attacker was involved.

A US embassy spokeswoman in Ankara said they were aware of an incident near the consulate and were investigating.