* Attacks on Sri Lankan mosques on the rise
* Tensions remain, elite police deployed
* U.S. calls for prosecution of perpetrators
* Bodu Bala Sena denies involvement in latest attack (Adds curfew, para 5; Muslim ministers' statement, para 12)
By Ranga Sirilal and Shihar Aneez
COLOMBO, Aug 11 (Reuters) - A Buddhist mob attacked a mosque in Sri Lanka's capital and at least 12 people were injured, the latest in a series of attacks on the minority Muslim community by members of the Buddhist majority.
A mob of Buddhists, who are mainly ethnic Sinhalese in Sri Lanka, threw stones at a three-storey mosque and nearby houses in a central Colombo neighbourhood during evening prayers on Saturday, residents told Reuters.
Later, hundreds of Muslim residents took to the streets, some clutching sticks, to prevent any further attacks on their community, witnesses said. Police reinforcements were sent and authorities imposed a curfew until Sunday morning.
A senior member of staff at one of the city's main hospitals said 12 injured people, including two police officers, had been brought in. Three people were still in hospital on Sunday.
Police appealed for calm and imposed a night-time curfew in the area.
"Support the police to maintain the law and order," Inspector General of Police N.K. Ilangakoon told state media.
There has been increasing violence against Muslims in Sri Lanka since last year, mirroring events in Buddhist-majority Myanmar, which has also seen a surge of attacks by members of the majority community against Muslims.
In Myanmar, hardline Buddhist monks have been at the forefront of campaigns against Muslims.
In Sri Lanka, a group known as Bodu Bala Sena (BBS), or the "Buddhist power force", has been trying to win over Buddhists to their campaign against Muslims.
A spokesman for the BBS, Dilantha Vithanage, denied any involvement by his organisation in the latest mosque attack.
Buddhists make up about 70 percent of Sri Lanka's 20.3 million population. Muslims make up about 9 percent.
"The lukewarm and ineffective measures taken by the law enforcement agencies on previous occasions ... seem to have emboldened some extremist groups who seem to determined to create chaos in the country," Muslim ministers in President Mahinda Rajapaksa's government said in a joint statement.
The mosque damaged in the Saturday night attack was only built a month ago after hardline Buddhists forced a nearby mosque to close.
The U.S. Embassy in Colombo said the incident was particularly troubling in light of a number of recent attacks against the Muslim community in Sri Lanka.
"Targeting any place of worship should never be permitted and we urge calm from all sides. We call for prosecution of perpetrators in this attack and an end to religious-based violence," the embassy said in a statement.
N. M. Ameen, president of Sri Lanka Muslim Council, said more than 20 mosques had been attacked since last year.
In a separate incident, a hand grenade was thrown at a Buddhist temple in the Jaffna peninsula, on the northern tip of the island. There were no injuries, police said.
Jaffna is largely made of ethnic minority Tamil people, most of whom are Hindu and Christian. The area was fiercely contested in a 26-year war between government forces and Tamil separatists that ended in 2009. (Editing by Robert Birsel and Jeremy Laurence)