“Following the bomb attacks in three churches in Surabaya, all areas in the Jakarta Police's jurisdiction have been placed under the highest alert status until further notice,” Jakarta Police chief Insp. Gen. Idham Azis said in a circular distributed to police stations in the capital.

East Java Police have confirmed that at least 10 people have died, while 41 others injured in a string of bomb attacks on three churches in the province's capital.

East Java Police, who have also declared siaga 1 status in their jurisdiction, have called on all churches to cancel services in Surabaya until the situation has been declared safe.

Riau Islands also raised its security alert status on Sunday morning.

Security has been tightened in areas where people are known to gather, especially in churches, Riau Islands Police chief Insp. Gen. Didid Widjanardi

“Riau islands has been placed under the highest alert level.”

Bali, meanwhile, has been under siaga 1 status since Tuesday evening, following a deadly riot involving terrorist inmates at a detention center located at the police’s Mobile Brigade headquarters (Mako Brimob) in Depok, West Java.

"We have intensified patrols and tightened security at the Bali Police headquarters and all police stations," he said.

Bali Police have urged people across the island to stay calm and vigilant following the terror attack in Surabaya on Sunday.

"Please reduce your activities in public areas for a while and always inform the nearest police if you see suspicious activity," Bali Police spokesperson Sr. Comr. Hengky Widjaja said.

He added that security at Bali's main entrances had also been tightened, including at I Gusti Ngurah Rai International Airport, Gilimanuk Port connecting Bali to Java island, Padangbai Port connecting Bali to Lombok island and other major and traditional seaports across Bali.

"We also tightened security in tourist areas, places of worship and other vital objects, including consulates in Bali," Hengky added. (ahw)