We are absolutely devastated ... whoever carries out this kind of daring attack will be captured and brought to justice

Erol Cakir, mayor of Istanbul

The Anatolia news agency reported that the bomber was 25-year old Ugur Bulbul, a member of the banned far-left Revolutionary People's Liberation Party-Front (DHKP-C).

Police have not confirmed this. Kurdish nationalists, extreme left-wing and Islamic groups, including the DHKP-C, have all carried out bombings in Turkey in the past.

Witnesses reported a large explosion with debris strewn across the street.

In the aftermath, police sealed off Taksim Square as bomb experts and ambulances arrived. An Australian tourist was also reportedly serious injured.

"I was driving along the other side of the road and suddenly there was an explosion ... I didn't see much else, but there were many people injured," said taxi driver Kemal Basmaki.

"It sounded like thunder, but lasted for just a second ... everybody round here heard it," said an American resident, who heard the blast from a few blocks away.

'A treacherous attack'

The Mayor of Istanbul, Erol Cakir, described the bombing as "a treacherous attack on the police".

Injured police officers were taken to hospital

"Whoever carries out this kind of daring attack will be captured and brought to justice," he added.

There were initial reports that the bomber was a woman, but the attack was later attributed to Mr Bulbul, who had apparently been recently released from prison.

The last suicide bombing in Istanbul, which has a population of 12 million, was in January, when a man walked into a police station and blew himself up, killing one officer and injuring seven people.

The DHKP-C claimed responsibility for that attack.