Indonesian policemen K-9 unit patrols with dog at the arrivals terminal at I Gusti Ngurah Rai International Airport ahead of Christmas and New Year holiday in Bali, Indonesia, December 20, 2018 in this photo taken by Antara Foto. Antara Foto/Nyoman Hendra Wibowo/ via REUTERS ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. INDONESIA OUT. NO COMMERCIAL OR EDITORIAL SALES IN INDONESIA.

JAKARTA (Reuters) - Indonesian police have detained about 20 suspected militants as security is stepped up ahead of the Christmas and New Year’s holiday season, a commander said on Thursday.

National police chief Tito Karnavian said the detentions were made preventively under a revised anti-terrorism law approved in May, after suicide bombings claimed by Islamic State killed more than 30 people in the city of Surabaya.

“There is no information yet about terror acts over Christmas and New Year’s but we are taking proactive steps including these arrests,” Karnavian told reporters.

Indonesia, the world’s largest Muslim-majority country, has struggled to contain a resurgence in militancy and scores of Indonesians have traveled to the Middle East to join the Islamic State group.

Near-simultaneous attacks on churches in the capital, Jakarta, and elsewhere on Christmas Eve in 2000, killed nearly 20 people. Ever since, authorities have stepped up security at churches and tourist spots for the holiday.

Karnavian did not identify any of the suspects but said they were detained in various parts of the country.

Under the revised law, anyone suspected of planning an attack can be held for up to 21 days for an initial inquiry and for up to 200 days for a formal investigation.