Hyderabad, India ? A bomb ripped through a historic mosque Friday in south India, 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 who were angered by what they said was a lack of police protection began chanting “God is great!” 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 clashes raised fears of wider Hindu-Muslim violence in the city, long been 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.

Many of the 35 people wounded were seriously hurt, and the city’s police chief, Balwinder Singh, warned the death toll could rise.

Y.S. Rajasekhara Reddy, the chief minister of Andhra Pradesh state, appealed for calm between Hindus and Muslims. He called the bombing an act of “intentional sabotage on the peace and tranquility in the country.”

Prime Minister Manmohan Singh echoed those sentiments in a statement released later.

“The prime minister has condemned the bomb blast in Hyderabad and has urged members of all communities to maintain peace and communal harmony,” his media adviser, Sanjaya Baru, said in the statement.