Sri Lankan police have arrested key suspects accused of fuelling religious riots and looting, as minority Muslims expressed fears of more unrest ahead of Ramadan, officials said.

Police said a total of eight people directly linked to the June 15 anti-Muslim riots were arrested this week and that they recovered gems and jewellery looted from two shops that were targeted during the violence.

"With the help of CCTV footage and the recently established (police) intelligence network we arrested the suspects along with the stolen goods", senior superintendent Athula Weerasinghe said on Saturday.

The violence, which erupted in the coastal resort of Alutgama, spilled over into the neighbouring international tourist resorts of Beruwala and Bentota.

Weerasinghe said jewellery worth more than $11,500 was recovered.

Officials estimate the riot damage at 200 million rupees. Four people were killed and 80 wounded in what were the worst religious riots in recent decades.

Sri Lanka's media as well as rights groups have accused the police of failing to prevent Buddhist mobs from attacking Muslims, who constitute 10 percent of the country's 20 million population.

Police, however, said investigations showed there was a strong criminal element that fuelled religious tensions. Earlier, police had arrested 55 suspects including both Buddhists as well as Muslims, but the eight arrested this week are the first to be held for looting and directly involved in attacking shops.

The announcement of the latest arrests came as the Muslim Council of Sri Lanka (MCSL), an umbrella group of 48 Muslim organisations, petitioned police chief N K Illangakoon expressing fears of more violence against their minority community during the holy fasting month of Ramadan.

"We are concerned that the root causes to the problems related to the attacks on the Muslim community and other minorities has not been addressed and appropriate action taken to enforce justice", the MCSL said.

MCSL president N M Ameen told the AFP news agency they would mark Ramadan in a low key fashion because of the fear of more hate attacks.

Facebook shutdown

Last week, Muslim-owned businesses shut down in Sri Lanka's capital to protest against deadly riots by Buddhists.

Muslims as well as a majority of moderate Buddhists have pressed for action against the Buddhist Force, or BBS, group which is seen as enjoying patronage of senior government figures.

In earlier reports on Friday, Buddhist activists accused of involvement in communal violence said that accounts of their group's members on social media site Facebook had been blocked.

"My account is blocked," Buddhist Force spokesman Dilantha Vithanage told Reuters by telephone. "I can't access my account. I last visited my account on June 25 and the accounts of others have also been blocked."

A Facebook spokesman in London declined to comment on any action taken by the company in Sri Lanka and referred Reuters to its terms of service.