Seven people, including the militants, were killed in Thursday's attack near the Sarinah department store in the Indonesian capital's commercial district
Indonesian police on Saturday named the five men they suspect launched this week's gun and bomb attack in Jakarta, which was claimed by ISIL, and said they had arrested 12 people linked to the plot who planned to strike other cities.
As investigators pieced together clues from the radical group's first attack on Indonesia, neighbouring Malaysia said it had arrested a man in Kuala Lumpur who had confessed to planning a suicide attack in the country.
"We ... have carried out acts of force. We have done searches, we have made arrests and we have obtained evidence connected with the terrorist bombing at Sarinah," Jakarta police spokesman Mohammad Iqbal told a news conference.
"We will not say how many people or what sort of evidence we have as it will upset out strategy. Be patient, when the case is closed and things are clear we will disclose them."
Seven people, including the militants, were killed in Thursday's attack near the Sarinah department store in the Indonesian capital's commercial district. About 30 people were hurt.
Police held up pictures of the dead and wounded at the news conference, including a man who kicked off the siege by blowing himself up in a Starbucks cafe.
Another attacker, who opened fire with a gun outside the cafe, was named as Afif. A National Counter-Terrorism Agency spokesman said Afif had served seven years in prison, where he refused to cooperate with a de-radicalisation program.
The brazenness of the Jakarta assault, which had echoes of marauding gun and bomb attacks such as the Paris siege in November, suggested a new brand of militancy in a country where extremists typically launch low-level strikes on police.
Police spokesman Anton Charliyan said the Jakarta five and the 12 others who were arrested had plans to attack cities elsewhere in Indonesia, including Bandung, which lies some 120 km (75 miles) southeast of the capital.
"There were general plans targeting certain places like police and government offices, foreigners or those cooperating with foreign entities," Charliyan told reporters.
Malaysian planned suicide attack
In Malaysia, the country's police chief said a suspected militant who was arrested in a metro station in Kuala Lumpur on Friday had confessed to planning a suicide attack.
Inspector-General of Police Khalid Abu Bakar said the 28-year-old Malaysian planned to carry out the attack in the country after receiving orders from a foreign member of ISIL in Syria.
"The suspect is also responsible for hanging IS flags at several locations ... to warn the government to stop arresting IS members in Malaysia," Khalid said in a statement.
No details were given about where and how he planned to attack.
Khalid said three other people suspected of being supporters of ISIL were arrested this week at Kuala Lumpur airport after they returned from Turkey.
Malaysia has been on high alert since Thursday's siege in Jakarta. Security has been beefed up in public areas and borders have been tightened to prevent jihadis getting into the country.
Earlier on Saturday, Indonesia said it had shut down at least 11 radical websites and several social media accounts, including several on Facebook that expressed support for the Jakarta attack.
"We are monitoring many websites and public complaints about this," said Ismail Cawidu, a public relations official at the communications ministry.
The government also sent letters to social media companies such as Facebook, Twitter and Telegram requesting radical material be immediately blocked or taken down, Cawidu said.
The alleged mastermind behind the Jakarta attack, an Indonesian citizen fighting with ISIL in Syria, is believed to have used social media extensively to share his beliefs about the group and communicate with contacts in Indonesia using blog posts and mobile messaging apps.
Authorities believe there are at least 1,000 ISIL sympathizers in Indonesia, which has the world's largest Muslim population.