Three unidentified gunmen and a Turkish policeman were reportedly killed in a shootout near the US consulate in Istanbul on Wednesday, the local news channel said. Three other policemen were injured in the exchange of fire, an unnamed witness said. The witness said three men, driving in a white car, opened fire at a police checkpoint near the consulate in the district of Istinye. The police returned fire, apparently killing all three gunmen, he said. There was no immediate official confirmation of the casualties.