Gunfire heard near entrance to Dolmabahce palace in Istanbul

Gunfire was heard on Wednesday near the entrance to the Dolmabahce palace in Istanbul, an Ottoman-era building popular with tourists which also houses the prime minister's Istanbul offices, the Dogan news agency said.

Turkish police detained two suspects with automatic weapons after a shooting on Wednesday near the entrance to Istanbul's Dolmabahce palace, popular with tourists and home to the prime minister's Istanbul offices, the Dogan news agency said.

Ambulances were sent to the area around the building and roads were sealed off by police, but there were no reports of casualties. Dogan said the attackers had targeted police officers stationed at the entrance to the palace.

Some local media reports suggested there had also been an explosion but there was no independent confirmation of this.

Prime Minister Ahmet Davutolgu was in the capital Ankara as reports of the attack emerged and did not interrupt a speech being broadcast on live television.

Turkey has been in a heightened state of alert since launching a "synchronised war on terror" last month, which included air strikes against Islamic State fighters in Syria and Kurdish militants in northern Iraq.

A fighter proclaiming allegiance to Islamic State appeared in a video this week urging Turks to rebel against "infidel" President Tayyip Erdogan and help conquer Istanbul, highlighting the threat to the NATO member state.

Turkey also faces a threat from far-leftist militants.

The leftist Revolutionary People's Liberation Army-Front (DHKP-C) claimed responsibility earlier this month for an attack on the US consulate in Istanbul, in which two women shot at the building. One of the attackers was hurt in an exchange of fire but there were no other casualties.