Indonesian officials have ordered increased security for Christian churches after attacks on two congregations Sunday evening.

Cabinet Secretary Sudi Silalahi said Monday that President Susilo Bambang Yudhoyono has ordered police to pay special attention to churches, especially during Christmas and New Year's.

Worshippers were inside the churches during Sunday's attacks in Palu, Central Sulawesi province. Police did not identify the attackers, but said they opened fire at one church and exploded a bomb at another.

Central Sulawesi has seen sporadic violence between Muslims and Christians since 1999, when sectarian fighting killed more than 1,000 people.

Four years ago, Christmas Eve bombings killed 19 people in churches across Indonesia.

Some information for this report provided by AP and Reuters.