A bomb ripped through a historic south India mosque Friday, and 13 people were killed — 11 in the blast and two in subsequent clashes between angry Muslim worshippers and security forces, police said.

Minutes after the blast at the 17th-century Mecca Masjid, worshippers angered by what they said was a lack of police protection began chanting "God is great!"

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A man injured in the bomb blast Friday is helped to the Osmania General Hospital in Hyderabad, India. ((Mahesh Kumar/Associated Press) )

Some hurled stones at police, who dispersed them with baton charges and tear gas.

While the situation at the mosque was quickly brought under control, Muslims later clashed with security forces in at least three parts of Hyderabad, said Mohammed Abdul Basit, police chief of Andhra Pradesh state, where Hyderabad is located.

Police fired live ammunition and tear gas to quell the riots, killing two people, he said.

The bombing, which killed 11 people and wounded 35, and the clashes raised fears of wider Hindu-Muslim violence in the city, long plagued by communal tensions— and occasional spasms of inter-religious bloodletting.

Authorities across India were told to be alert for any signs of Hindu-Muslim fighting, and top officials called for calm.

Indian Prime Minister Manmohan Singh condemned the bombing, the second of a mosque in a year, and "urged members of all communities to maintain peace and communal harmony," his office said in a statement.

Y.S. Rajasekhara Reddy, chief minister of Andhra Pradesh, called the bombing an act of "intentional sabotage on the peace and tranquility in the country."

Reddy told reporters in New Delhi, where he was meeting with federal officials on unrelated business, that one bomb went off around 1:30 p.m. local time, and that police soon after found and defused two other bombs in the area of the mosque.

The bomb, made of a stick-grenade packed into a metal pipe, was detonated by a mobile phone attached to the device, said Basit.

Neither he nor any other officials gave any indication of who they suspected in the attack.

Hindu-Muslim relations tested

About 10,000 people usually attend Friday prayers at the mosque in a Muslim neighbourhood of Hyderabad. The explosion sparked a panic.

"I was very close to the spot of the blast," said Abdul Quader, 30, who sustained light injuries to his legs.

"As soon as prayers ended, we were about to get up. There was a huge, deafening blast sending bodies into the air," he said. "People started running helter-skelter — there was such confusion. People were bleeding, running around in a very bad condition."

Relations between Hindus, more than 80 per cent of India's population of 1.1 billion, and its 130 million Muslims, have been largely peaceful since the bloody partition of the subcontinent into India and Muslim Pakistan at independence from Britain in 1947.

However, there have been sporadic bouts of violence.

The worst in recent years came in 2002, in the western state of Gujarat. More than 1,000 people, most of them Muslim, were killed by Hindu mobs after a train fire killed 60 Hindus returning from a religious pilgrimage. Muslims were blamed for the train fire.

The Hyderabad bombing came the same day a judge in Mumbai began sentencing those convicted of involvement in India's worst terror attack, the 1993 Mumbai serial bombings that killed 257 people.

The bombings were believed to have been acts of revenge by Muslims for the demolition of the Babri Mosque and ensuing riots that left more than 800 dead, most of them Muslims.