A bomb attack targeted Turkish police in a central Istanbul district on Tuesday, leaving several people wounded, the state-run TRT television reported.
The remote-controlled bomb exploded as a service shuttle carrying police officers was passing in the Beyazit district of Istanbul, the TRT reported.
Ambulances and fire engines were dispatched to the scene. Five people were injured according to initial findings, the Dogan news agency reported.
Reports said the explosion took place close to the Vezeciler metro station, which is within walking distance of some of the main sights of the historical centre including the Suleymaniye Mosque.
Pictures showed that nearby shops had their front windows smashed out by the force of the blast.
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 aimed at a military vehicle in Istanbul that was claimed by the PKK.
Meanwhile, a dozen German tourists were killed on January 12 in a bombing in the heart of Istanbul's tourist district blamed on Islamic State jihadists.
At least three Israelis and an Iranian were killed in a March 19 bombing on Istanbul's main Istiklal shopping street which was also blamed on IS jihadists.
The attacks have also come as Turkey is battling PKK militants, who have themselves killed hundreds of members of the security forces in the southeast.
The government has warned there will be no let-up in the fight until the PKK is defeated and the militants have in turn threatened more attacks.
But the attacks in Turkey's heartland have had a dire effect on the tourism industry and further violence in Istanbul comes at the worst possible time heading into the key summer season.
Some 1.75 million foreigners came to Turkey in April, down more than 28 percent on April 2015, the tourism ministry said in its latest release.
The fall was the steepest monthly decrease for 17 years and raised fresh concerns about the health of the industry heading into the crucial summer season.
The US embassy in Turkey in April warned of "credible threats" to tourist areas in Istanbul and the resort city of Antalya, in particular to public squares and docks.