Worshippers at two Malaysian mosques discovered severed pig heads in the buildings Wednesday as religious tensions in the multi-ethnic nation threatened to escalate.

The incidents at the mosques, located in an ethnic Malay-dominated suburb of the capital, Kuala Lumpur, raised fears that already strained relations between Malaysia's majority Muslim population and its large minorities of Christians, Hindus and Buddhists would be further aggravated.

Police chief Musa Hassan said unknown culprits had thrown the severed heads into the mosques and urged people of all religions not to react to the incident.

Pigs are considered offensive animals to Muslims, who are forbidden to consume pork, and coming into contact with the animal renders a Muslim unclean.

'We will meet with heads of all religious groups in the district to seek their assistance to cool things down,' Musa was quoted as saying by the Star newspaper.

'I have directed that extra patrols be conducted at places of worship throughout the country,' he said.

Over the past few weeks, 11 churches, a Catholic school, a Sikh temple, two mosques and two Muslim prayer rooms have been hit by arson and vandalism attacks in an escalating row over the use of the word Allah by Christians.

A High Court ruling Dec 31 had overturned a government ban forbidding the use of the word in non-Muslim publications and said the Herald, a Roman Catholic newsletter, was permitted to use it in its Malay-language publications.

The government has appealed the decision, maintaining that Muslims would be confused if the word Allah was used by people of other religions.

However, Christians have argued that the word is common among their Malay-speaking believers, who account for about 10 percent of the country's 28 million people, and banning its usage would be unconstitutional.

Malaysia's largest ethnic group is the Malays, who make up 60 percent of the population and are almost exclusively Muslims.

While Islam is Malaysia's official religion, the country's constitution protects the rights of other religions.

Minority religious groups have often complained of marginalisation and have expressed fears of increasing Islamisation policies undertaken by the government.