Turkish police have detained four suspects over a car bombing in Istanbul that killed 11 people, including seven police officers, local media reports say.

Key points: There was no early claim of responsibility for the attack

There was no early claim of responsibility for the attack There have been several attacks in Turkish cities in the past year

There have been several attacks in Turkish cities in the past year Blast caused damage to nearby cars and buildings

The suspects were taken to the city's police headquarters for interrogation, the state-run Anatolia news agency said, without providing further information.

The car bomb was detonated as a police bus was passing through the central Beyazit district, close to many of the city's top tourist sites, Istanbul's governor Vasip Sahin said.

The blast killed at least seven members of the rapid response unit and several civilians, while at least 36 people were wounded, three of them seriously, he added.

There was no early claim of responsibility, but President Recep Tayyip Erdogan hinted the outlawed Kurdistan Workers' Party (PKK) was behind the attack.

For the PKK to target major cities such as Istanbul "is nothing new," he said after visiting the injured at an Istanbul hospital.

"We will fight against terrorists relentlessly to the end."

The bomb reduced the police vehicle to mangled wreckage and the windows of nearby shops were blown out by the force of the blast.

Sorry, this video has expired Aftermath of the deadly bomb blast in Istanbul

Local shopkeepers said the blast was followed by gunfire, and cars parked in the vicinity were also damaged.

The blast took place opposite an upscale hotel favoured by foreign tourists, the Celal Aga Konagi Hotel, a converted Ottoman mansion.

The loudspeakers on mosques were used to warn people to vacate the area, after which a controlled explosion was carried out on a suspicious vehicle.

Series of attacks impacting tourism industry

Since the start of the year, Turkey has been hit by a sequence of attacks that have rattled citizens and also caused tourism to plummet.

Two separate blasts in Ankara claimed by the Kurdistan Freedom Falcons (TAK) — a radical splinter group of the better-known outlawed Kurdistan Workers' Party (PKK) — earlier this year claimed dozens of lives.

Last month, at least eight people including soldiers were wounded by a remotely detonated car bomb targeting a military vehicle in Istanbul that was claimed by the PKK.

Turkey has stepped up its military campaign against PKK militants in the southeast of the country and in neighbouring Iraq.

On January 12, a dozen German tourists were killed in a bombing in the heart of Istanbul's tourist district blamed on Islamic State.

Two months later, three Israelis and an Iranian were killed in a bombing on Istanbul's main Istiklal shopping street, which was also blamed on IS.

The violence has had a devastating effect on the tourism industry, with the latest attack coming at the worst possible time, at the outset of the key summer season.

Some 1.75 million foreigners came to Turkey in April, down more than 28 per cent on April 2015 — the steepest monthly decrease for 17 years.