Turkish Prime Minister Ahmet Davutoglu denounced the suicide bombing that killed five people and wounded 36 in Istanbul on Saturday as "inhumane".
He said Turkey would continue its struggle against "centres of terrorism".
At least one Iranian and two Israelis are among the dead from the suicide bombing in Istanbul.
Five were killed in the attack - including the suicide bomber - and 36 were injured - including a number of Irish citizens.
The attack took place on Istiklal Street, home to upscale shops and foreign consulates.
Two buildings - one of which was a five-storey - have collapsed in Istanbul close to the Turkish city's main shopping area.
At this stage there has been no report of casualties.
Local governor Vasip Sahin told CNN Turk no one is believed to have been killed or injured.
Turkish riot police clashed with anti-government protesters in central Istanbul on the anniversary of the country's biggest anti-government demonstrations in decades.
The police fired teargas and water cannon to disperse the protests and detained dozens of demonstrators.
Authorities closed roads and stopped public transport to deny the protesters access to Taksim Square and the adjoining Gezi Park.The government plans to raze the park and build a shopping mall sparked last year's unrest.
Turkey's Prime Minister Tayyip Erdogan warned people to stay out of Taksim, saying security forces would not tolerate any march on the square.
Turkish police have fired teargas to disperse hundreds of people protesting against the police crackdown on last month's anti-government demonstrations, local media reports.
Police blocked several hundred protesters near Istanbul's Taksim Square from marching in support of a teenage boy said to be in a coma after being hit in the head by a teargas canister during the unrest.
TV footage showed police vehicles shooting water cannons while protesters flee.
Nationwide protests against Prime Minister Tayyip Erdogan last month have largely died down across the country, but some isolated demonstrations have continued in Istanbul and the capital, Ankara.
One protester in the Turkish city if Istanbul managed to wedge himself between the windscreen and bonnet of a water cannon truck.
Out of the reach of the stream of pressurised water, he was able to unfurl a Turkish flag directly in front of where the drivers were sitting.
Turkey's trade union confederation KESK has called a general strike for Monday after a police raid on a protester camp in Istanbul's Gezi Park this evening.
Police wielding tear gas and water cannon are locked in an ongoing struggle with anti-government demonstrators for control of the park and adjoining Taksim Square.
Police are using water cannon and tear gas against protesters in Istanbul's Taksim Square and adjoining Gezi Park.
The move comes just hours after Turkey's Prime Minister Recep Tayyip Erdogan told a rally in Ankara: "Taksim Square must be evacuated, otherwise this country's security forces know how to evacuate it".
An uneasy calm hangs over Taksim Square - the epicentre of Turkey's protest movement - after clashes between demonstrators and riot police overnight left dozens injured.
Riot police and water cannon are on standby in the square in case of further disturbances and journalists on the ground say work is continuing to remove barricades.
Protesters have constructed a makeshift camp in the adjoining Gezi Park and most appeared to be resting after last night's ordeal.