COLOMBO (AFP) - Sri Lanka boosted security for Muslim-owned businesses across the country on Friday after a clothing store was torched by hundreds of Buddhist hardliners, escalating religious tensions.

Police said commandos of the elite Special Task Force were deployed in the Colombo suburb of Pepiliyana where mobs from the ethnic Sinhalese majority stoned and later set fire to a store and warehouse owned by Muslims late on Thursday.

"We are deploying more mobile patrols in vulnerable areas" across the country, a senior police officer told AFP, declining to be named. He said extra police would be guarding popular Muslim-owned shops.

The government in a statement urged people not to be provoked.

"Be aware of anti-democratic, extremists and terrorist forces destroying public and private property," the government's information department said. "Do not fall prey to divisive forces aiming to destabilise Sri Lanka."

The key Muslim coalition partner in President Mahinda Rajapakse's government, the Sri Lanka Muslim Congress (SLMC), urged him to "take proactive action to stop this spread of religious attacks and intolerance".

The SLMC said they were treating Thursday's violence as a "sequel to the ongoing attacks and hate campaigns" against Muslims and other religious minorities in the country.

The authorities have not declared a motive for the attack that injured at least three people, but official sources said Sinhala-Buddhist hardliners were responsible.

However, the recently formed Buddhist nationalist group, the monk-led Bodu Bala Sena (BBS), denied involvement and urged authorities to bring the perpetrators to justice.

"We condemn this attack in the strongest terms," BBS spokesman Galaboda Aththe Gnanasara told reporters in Colombo, saying he feared that people impersonating the saffron-robed clergy could have been involved.

The BBS last month forced Islamic clerics to withdraw halal certification from food sold locally, claiming that it offended the majority non-Muslim population.

But Mr Gnanasara said the BBS was only against Islamic extremism.

The Muslim Council of Sri Lanka, an umbrella organisation of Muslim groups, said tensions had been ratcheted to a new high by Thursday's attack.

"It has created a fear psychosis among the Muslims," council president NM Ameen told AFP. "We know a majority of the (Buddhist) people do not support this type of activity."

Army units were called in to disperse Thursday's mob, who pelted stones, smashed parked vehicles and torched clothing at the Fashion Bug store.

"The situation was brought under control within a few hours," said police spokesman Buddhika Siriwardena, adding that three members of the majority Sinhalese community were arrested and a search was on for several others.

It came a day after Sri Lankan police set up a hotline to tackle complaints about anyone suspected of "inciting religious or racial hatred".

In January, mobs hurled stones at another Muslim-owned clothing chain near Colombo, while Muslim businessmen have also complained of random stone-throwing, intimidation and calls for boycotts of their shops.

President Rajapakse, who is a Buddhist, urged monks earlier this year not to incite religious hatred and violence.

The United Nations estimates that Sri Lanka's ethnic civil war claimed at least 100,000 lives between 1972 and 2009, when Tamil separatist rebels were crushed in a major military offensive.

Less than 10 per cent of Sri Lanka's population of 20 million are Muslim. The majority are Sinhalese Buddhist, while most Tamils are Hindu.