Malegaon, India ? Two bombs rigged to bicycles exploded in throngs of Muslims as they left Friday prayers at a mosque in this western Indian city, killing 31 people and wounding 100.

A top official called the blasts “a terrorist act,” and authorities – fearing revenge attacks across the country’s fragile religious divides – clamped a curfew on Malegaon and put security forces on alert.

Late Friday, the city’s streets were empty, with thousands of police on patrol and checkpoints set up around the perimeter.

Malegaon, a center of India’s textile industry about 180 miles northeast of Mumbai, has long been the scene of violence between Hindus and Muslims.

While it was unclear who was behind the bombings, which happened near one of the city’s main mosques on a Muslim festival day, officials aggressively deployed teams of police to sensitive parts of the state.

“Law and order is under control,” P.S. Pasricha, Maharashtra state’s director-general of police, told The Associated Press. “There’s a high alert across the state. We have activated all police machinery to ensure that communal harmony is maintained.”

Malegaon, a city of about 500,000 that is 75 percent Muslim, is in Maharashtra state.

The bombings were intended to set off wider violence, officials said.

“It is a terrorist act. It is done by people who don’t want peace,” Maharashtra Chief Minister Vilasrao Deshmukh told a news conference in Mumbai, the state capital. Of the 100 people wounded, he said, 56 were seriously hurt.

A jeep lies upturned and on fire Friday after an explosion in Malegaon, India. A pair of bombs rigged to bicycles killed 31 people and injured 100, a top official said.

Pasricha told reporters “the motive appears to be to create panic and make Hindus and Muslims fight with each other.” He also spoke in Mumbai, formerly known as Bombay.

Both bombs were rigged to bicycles, said Deshmukh. “We found packets with the explosives attached to these bicycles,” he said.

The explosions came as Muslims celebrated the festival of Shabe Barat, or the Night of Fortune, when they hold night-long prayers seeking divine blessings, exchange sweets with neighbors and relatives, and set off fireworks.

At least some of those killed were beggars who came to the mosque because worshippers are known for their generosity on festival days, said Raees Rizvi, a Malegaon social worker.

He said community leaders had been meeting with authorities since the blasts, in an effort to stop further violence.

“This was to spread tension in the area,” said Raees Rizvi.

The city’s fear, though, was evident – with many streets empty of everyone but police, and few people willing to speak to a reporter.

The office of Prime Minister Manmohan Singh said he “appealed for peace and communal harmony and has urged all citizens across the country to remain calm.”

India has suffered through a series of terror bombings during the past year, most recently attacks on commuter trains in July in Mumbai that left more than 200 people dead. Those bombings were blamed on Pakistan-based Muslim militants.