COLOMBO (AFP) - Sri Lanka's police arrested three Buddhist monks on Monday over the smashing of a Muslim-owned clothing store that heightened religious tensions in the country, an official said.

Police superintendent Buddhika Siriwardena said the monks were detained four days after a mob of Sinhalese-Buddhist men vandalised and torched a section of the three-storey building in the Pepiliyana suburb of Colombo.

"Three monks were arrested after they surrendered today," police spokesman Buddhika Siriwardena told AFP. "They will be taken before a magistrate tomorrow. We are looking for more suspects."

Officials said the monks were among 17 held in connection with Thursday's attack which the main Muslim party in the ruling coalition said was a "sequel" to an ongoing hate campaign against Muslims and other religious minorities.

The owners of the clothing store, Fashion Bug, said the attack had "shocked and disturbed us a great deal and instilled fear in the minds of our staff members in carrying out their day to day work".

Muslims, who constitute about 10 per cent of the country's 20 million population, are the second largest minority after the mainly Hindu ethnic Tamils. Seventy per cent of the population are Sinhalese, most of whom are Buddhists.

Thursday's attack, which raised fears of safety among Muslims, was followed by another incident, this time against the main Tamil political party, in the island's north on Saturday.

The opposition Tamil National Alliance (TNA) said their meeting in the town of Kilinochchi on Saturday was disrupted by a stone-throwing mob which had also attacked their vehicles and damaged a building while police looked on.

The military denied that security forces were involved in Saturday's attack and insisted that the police had prevented a further escalation.

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 by government forces.