JAKARTA (AFP) - Indonesian police said on Thursday (June 9) they have arrested three Muslim extremists who were planning to launch ISIS-inspired suicide bombings in the country's second-biggest city.

The police's elite anti-terror squad detained the men in Surabaya, on the country's main island of Java, on Wednesday and seized bombs and firearms, said national police spokesman Boy Rafli Amar.

He said the group planned to attack public places and government offices in the city in the coming weeks, without giving further details.

"The were influenced by IS on social media," Amar said, referring to Islamic State in Iraq and Syria militants, who have declared a "caliphate" in large areas of territory that they have seized in Iraq and Syria.

"They were inspired by IS leaders' speeches." Police said one of the detained men had links to Abu Jandal, an influential Indonesian militant fighting with ISIS in Syria, but did not give further details.

Analysts say that Jandal and other Indonesians in Syria have been competing to impress ISIS's leaders by encouraging their followers back home to launch attacks, and have on occasion provided funds and guidance.

A second suspect had been jailed for drugs offences in the same prison as several convicted militants. Jails are considered hotbeds of radicalism in Indonesia.

Police did not give details on the third man.

Amar said the men were not involved in a suicide bombing and gun attack in Jakarta in January, that left four civilians and four attackers dead and was claimed by ISIS.

Indonesia, the world's most populous Muslim-majority nation, has suffered several Islamic extremist attacks in the past 15 years, including the 2002 Bali bombings that killed 202 people.

A crackdown had weakened the most dangerous networks, but the emergence of ISIS has proved a potent new rallying cry for radicals.

Hundreds of Indonesians have travelled to the Middle East to join the militants, stoking fears that extremist groups are being revived and more attacks could be on the horizon.