BALI – Police on the Indonesian resort island of Bali have detained five Indonesians returning from Turkey on suspicion they travelled abroad to join the Islamic State group, an official said Thursday.

Bali police spokesman Hengky Widjaja said the three men and two women were detained after they arrived in Bali on an Emirates flight from Istanbul on Tuesday evening.

He said the group was nabbed at a ”safe house” on Jan 16 by Turkish soldiers.

It was the second batch of Indonesians detained this month after returning from Turkey, which has a porous border with Syria where IS militants control territory.

Last week, authorities detained 17 people, including eight women, as they arrived at Jakarta’s Soekarno-Hatta International Airport.

Mr Widjaja said the five, all from northern Jakarta, left Indonesia last Aug 15 for Thailand to avoid raising suspicion in Indonesia. From Thailand, they flew to Istanbul, he said.

Indonesian authorities have heightened surveillance at border checkpoints following a series of foiled plots by IS supporters in Indonesia.