A Syrian suicide bomber struck the heart of Istanbul's busiest tourist district, killing 10 people, a lot of them Germans, in the latest deadly attack blamed on Islamic State jihadists.

Ten tourists were killed during the suicide bomb attack Tuesday at Istanbul's historic Sultanahmet Square, a popular tourist destination.

Turkish authorities arrested a number of suspected Islamic State militants during raids Wednesday, including three Russian nationals.

Police also seized documents and CDs during a search of the premises where the suspects were staying, according to one news agency.

Turkey was quick to identify the bomber, named by Turkish media as 28-year old Saudi-born Nabil Fadli, as the man who had given his fingerprints a week ago at an immigration center.

German Chancellor Angela Merkel condemned on Tuesday the alleged terrorist attack in Istanbul that killed more than 10 people, including German citizens.

Davutoglu said that the bomber had not been on any wanted lists, but was registered entering Turkey from Syria as one of over 2.2 million Syrian refugees fleeing their nation's nearly five-year civil war.

The guide of the German group was quoted by Turkey's Hurriyet newspaper as saying she had yelled "run" after seeing the bomber, who was standing among the tourists, pull a pin on his explosives, enabling some of them to get away.

German Interior Minister Thomas de Maiziere has meanwhile said there was no suggestion that Tuesday's suicide attack specifically targeted Germans.

The Islamic State and other militant factions have waged similar attacks targeting tourist sites in other countries, including an armed siege of Tunisia's renowned Bardo Museum last March that claimed more than 20 lives, many European visitors.

The attack on Westerners rattled Turkey's leaders, who said they have been carrying out security operations around the country in an effort to thwart this kind of attack.

Germany's interior minister says there are no indications so far that Germans were specifically targeted in the attack in Istanbul.

Turkey has faced increased violence in recent months generated by the Islamic State and after a ceasefire broke down between the Turkish government and PKK Kurdish rebel militants - which led to airstrikes by Turkey and bombings by rebels.

Germany sent a team of investigators to Istanbul from its Federal Criminal Police Office to support Turkish authorities investigating the attack. Germany already was helping supply and train Kurdish forces fighting the IS group in northern Iraq.

Officials initially said that at least eight Germans were among the dead in the explosion.

Ala said Turkey had detained 3,318 people for suspected links to Islamic State and other radical groups since Syria's conflict began.

"Turkey will continue to punish with even greater force any threat that is directed against Turkey or its guests", Davutoglu said.