Farouk Arnaz & Heru Andriyanto, Jakarta – Armed men who attacked a subdistrict police station in Medan in the early hours of Wednesday, killing three officers, are linked to the group that committed a bloody bank heist in the same city, police said.

"They are linked to the CIMB Niaga bank heist. They demonstrated a similar pattern of attack and they seemed to be well-trained," National Police spokesman Insp. Gen. Iskandar Hasan told the Jakarta Globe.

National Police Chief Gen. Bambang Hendarso Danuri said raids by the elite Densus 88 antiterror police unit in North Sumatra on Sunday prompted the revenge attack. The weekend raids left three suspects dead while 15 others were arrested.

According to Bambang, the suspects are connected with an Aceh-based terrorist group, and were also responsible for a spate of robberies in the region, including the deadly Aug. 18 CIMB Niaga robbery.

"At first they targeted foreigners, then they robbed to get money to finance their movement and now they have gathered the courage to attack a police station," he said.

Security experts were also quick to speculate that Wednesday's attack was in revenge for the three men killed in Sunday's police raids.

"In my opinion, this is outright retaliation. There is an ideology called qishas, or an eye for an eye," security expert Noor Huda Ismail said.

Intelligence analyst Dynno Cresbon said the attack was most likely masterminded by terror fugitive Abu Tholut.

"The attack fits the style of Abu Tholut, who always deploys a group of men with assault rifles," Dynno said. "In this regard, he differs himself from Noordin Moh Top or Azahari who preferred to recruit suicide bombers."

"The Abu Tholut group sees police as their target, and that isn't a recent thing. Remember the attack on a police post in Purworejo [Central Java] in April. He is believed to have been responsible for that attack too," he said.

Al Chaidar, a terrorism expert from Malikussaleh University in Aceh, said the attack carried Tholut's signature, but he doubted that it was motivated by revenge.

"Abu Tholut has the skills for guerilla tactics and robbery. But I think the series of attacks involving his group were born from careful planning," Al Chaidar said, adding that the preparations for the early morning raid on the police station would probably have taken months. "It won't be surprising if they expand their attacks to military targets," he warned.

[Additional reporting from Kinanti Pinta Karana & Candra Malik.]