Four Malaysian churches have been firebombed in the capital, Kuala Lumpur, with one of them being extensively damaged.
The attacks came just hours before Muslim groups held protests over the use of the word "Allah" by non-Muslims.
Some Muslim groups believe that a recent court ruling allowing non-Muslims to use the word to refer to God is part of a plan to encourage Muslims to convert to Christianity.
The government of the predominantly Muslim country has condemned the attacks and vowed to take action. Police security has been stepped up around churches but no arrests have been made so far.
Newspaper used word after ban lifted
The BBC reports that the controversy stems from a ban on a Catholic newspaper, the Herald, using the word "Allah" in its Malay-language edition.
This came after the Kuala Lumpur High Court had struck down a three-year-old ban on non-Muslims using the word.
The government has appealed against the verdict. About 60% of Malaysians are Malay Muslims and the government relies on their vote.