Police in Turkey say two gunmen from an illegal leftist organisation have been shot and killed during a clash in the Tepebasi district of Istanbul.

The police say the two were armed with guns and a shoulder-mounted rocket launcher and were believed to be preparing to attack the United States consulate in the city.

The Istanbul police chief, Hasan Ozdemir, said security officials had been tipped off about a possible attack and had increased patrols in the area.