More than 43,000 Malaysians protested online over a court ruling allowing a Catholic paper to use the word Allah to describe the Christian God, signaling growing Islamic anger in this mostly Muslim Southeast Asian country.

A group page on social networking site Facebook was drawing 1,500 new supporters an hour on Monday as last week's court ruling split political parties and even families.

Among those who signed up for the protest were Deputy Trade Minister Mukhriz Mahathir, the son of Malaysia's longest serving prime minister, Mahathir Mohamed, while Mahathir's daughter Marina called critics of the court decision idiots in her weblog (http://rantingsbymm.blogspot.com/)

The government said on Monday it had filed an appeal against the court ruling amid concerns the issue could cause religious and racial conflict in this country of 28 million which has large Christian, Buddhist and Hindu minorities.

The problem is that there will be lots of doctrines and principles promoted that would totally contradict Islamic theology... there is a danger to public order here, said Shad Saleem Faruqi, a constitutional law lecturer with Universiti Tekonologi Malaysia.

The Facebook page, named in Malay as Protesting the use of the name Allah by non-Muslims, said that the group was for Muslims who realize that this is propaganda to confuse Muslims now and in future.

The Catholic Church, which publishes a Malay version of its newspaper, The Herald, says that it uses the word Allah for the Christian God to meet the needs of its Malay speaking worshippers on the island of Borneo.

There should not be a cause for concern because some people have got the idea that we are out to convert (Muslims), but not at all, there is no question of this, Father Lawrence Andrew, the newspaper's editor, told Reuters.

The ruling by the Kuala Lumpur High Court followed a ban imposed by the government on the weekly Herald in January last year over the use of the word Allah by Christians.

The government had argued that the use of the Arabic word might offend the sensitivities of Muslims who make up 60 percent of Malaysia's 28 million population, while Christians -- including about 800,000 Catholics -- make up about 9.1 percent.

The Herald circulates in Sabah and Sarawak on Borneo Island where the indigenous population converted to Christianity more than a century ago and where the word has been commonly used in prayer for decades.

Malaysia's ethnic Chinese and Indian communities abandoned the ruling coalition in the 2008 general elections in part due to unease over an increasing Islamization in the country.

In 2008, the government that has ruled Malaysia for 52 years suffered its worst ever results in national and state elections and Prime Minister Najib Razak has sought to address the fears of minority groups by adopting an inclusive racial program called 1Malaysia.

Najib has appealed for calm pending the appeal but the government, like the country's three-party opposition grouping, is wary of upsetting the Malays, who form a critical vote bank.

Mahfuz Omar, the vice-president of the opposition Pan Malaysian Islamic Party (PAS), said the main government party, the United Malays National Organization (UMNO), was politicizing the issue.

This shows that UMNO is taking opportunity on this issue to whip up Muslim sentiment so that they unite and see UMNO as the champion of Islam, said Mahfuz in a statement on Monday.

(Reporting by Razak Ahmad; Editing by Nick Macfie)