HYDERABAD, India: Indian police investigating a dual bomb attack that killed 15 people outside a movie theater and a bus station in the southern city of Hyderabad were searching for links to a shadowy Islamic militant group with reported ties to Pakistan, an official said Friday.

Officials were examining whether the Indian Mujahideen, which is thought to have a link with militants in neighboring Pakistan, might have carried out the attack, an investigator told The Associated Press, speaking on condition of anonymity because he was not authorized to reveal details of the probe. India's recent execution of an Islamic militant is being examined as a possible motive for the bombings, he said.

Police have not yet detained anyone in connection with the Thursday evening attack, the first major terror bombing in India since 2011.

Home Minister Sushilkumar Shinde said there was a general alert about the possibility of an attack somewhere in India for the past three days. "But there was no specific intelligence about a particular place," he said as he toured the site Friday morning.

The bombs were attached to two bicycles about 150 meters (500 feet) apart in Hyderabad's Dilsukh Nagar district, Shinde said. He said in addition to the dead, 119 others were injured.

The bombs exploded minutes apart in a crowded shopping area. The blasts shattered storefronts, scattered food and plates from roadside restaurants and left tangles of dead bodies. Passersby rushed the wounded to hospitals.

"This is a dastardly attack; the guilty will not go unpunished," Prime Minister Manmohan Singh said. He appealed to the public to remain calm.

Top state police officer V. Dinesh Reddy said improvised explosive devices with nitrogen compound were used in the blasts, which he blamed on a "terrorist network."

On Friday morning, police with cameras, gloves and plastic evidence bags used pointers to gingerly look through the debris. Officials from the National Investigation Agency and commandos of the National Security Guards arrived from New Delhi to help with the investigation.

India has been under a heightened state of alert over the hanging of Mohammed Afzal Guru, a Kashmiri militant nearly two weeks ago. He was executed for his involvement in a 2001 attack on India's Parliament that killed 14 people, including five of the gunmen.

Since the execution, near-daily protests have rocked Indian-ruled Kashmir, where many people believe Guru did not receive a fair trial. Anger in a region where anti-India sentiment runs deep was further fueled by the secrecy with which the execution was carried out.

Mahesh Kumar, a 21-year-old student, was heading home from a tutoring class when one of the bombs went off.

"I heard a huge sound and something hit me, I fell down, and somebody brought me to the hospital," said Kumar, who suffered shrapnel wounds.

Hyderabad, a city of 10 million in the state of Andhra Pradesh, is a hub of India's information technology industry and has a mixed population of Muslims and Hindus.

"This (attack) is to disturb the peaceful living of all communities in Andhra Pradesh," said Kiran Kumar Reddy, the state's chief minister.

The explosions were the first major terror attack in since a September 2011 blast outside the High Court in New Delhi killed 13 people. The government has been heavily criticized for its failure to arrest the masterminds behind previous bombings.

The attack was the second bombing in the Hindu-dominated area, following a 2000 blast outside a Hindu temple that killed two people. In 2007, a twin bombing killed 40 people in two other Hyderabad districts.

The United States, whose Secretary of State John Kerry was meeting Thursday in Washington with Indian Foreign Secretary Ranjan Mathai, condemned the attack.

"The United States stands with India in combating the scourge of terrorism and we also prepared to offer any and all assistance Indian authorities may need," State Department spokeswoman Victoria Nuland told a news briefing.

Rana Banerji, a former security official, said India remains vulnerable to such attacks because there is poor coordination between the national government and the states. Police reforms are also moving very slowly and the quality of intelligence gathering is poor, he said.

"The concept of homeland security should be made effective, on a war footing," he said.