ISTANBUL - Turkey said Wednesday it had arrested a total of five suspects over a deadly suicide bombing carried out by an Islamic State (IS) jihadist that killed 10 German tourists in the historic centre of Istanbul.

Ankara has said that Tuesday’s strike was perpetrated by a 28-year-old Syrian who belonged to the IS group and had recently entered Turkey from Syria as a migrant.

Prime Minister Ahmet Davutoglu said that four suspects had been arrested Wednesday in relation to the attack. Interior Minister Efkan Ala said earlier that one person had already been arrested on Tuesday in connection with the bloodshed.

Turkish security forces over the last days also rounded up 74 suspected IS members across the country, state media said, but it was not clear if any were directly connected to the Istanbul bombing. 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 almost five-year civil war.

“This person was not being followed (as a wanted suspect). This person entered Turkey as an ordinary migrant,” said Davutoglu. “All his links will be worked out now.” “Turkey is working to find the true actors behind this attack where Daesh (IS) was used as a subcontractor,” he added, without explaining further.

The bomber, identified as Nabil Fadli, detonated his charge in Sultanahmet Square, home to Turkey’s most visited historic sites including the Ottoman-era Blue Mosque and Hagia Sophia church. The explosion went off by the Obelisk of Theodosius, a monument from ancient Egypt, one of the city’s most iconic landmarks.