A string of 12 bomb blasts tore through the main city of India's troubled northeastern Assam state and three other towns on Thursday, killing at least 61 people and wounding more than 300, police said. No one claimed responsibility for the attacks. Assam has been a focus of a separatist insurgency for decades, but it has also recently suffered bomb attacks blamed on Islamist militants from neighboring Bangladesh. Intelligence agencies are ascribing the blasts to the separatist United Liberation Front of Assam (ULFA) or Harkat-ul-Jehad-al-Islami (HUJI), a Bangladesh based outfit, which has been blamed for a number of terrorist incidents in the country. ULFA released a statement denying involvement in Thursday's blasts, most of which were in crowded markets. Many bombs were hidden in motorcycles or scooters. “The area was teeming with people, office workers, shoppers and vendors when a very big explosion took place,” said witness Arindam Das, who was shopping in one of the targeted markets in state capital Guwahati. The blasts, including one in front of the Guwahati District Magistrate's Court, were powerful enough to reduce nearby vehicles to a heap of twisted metal. “Some of the bodies were charred beyond recognition,” Deputy Inspector General of Assam Police G.P. Singh said. Thirty-one people were killed in Guwahati, with 19 dead in the Assam's western district of Kokrajhar and 11 in nearby Barpeta town, officials said. Assam state Chief Minister Tarun Gogoi told a news conference that 75 of the wounded in the blasts were critically injured. An immediate curfew was clamped on Guwahati as angry residents went on the rampage, attacking police vehicles, fire engines and even ambulances. Police fired in the air to disperse the angry mob. Indian Prime Minister Manmohan Singh called for calm and said every effort would be made to bring the bombers to justice. “Such barbaric acts targeting innocent men, women and children only highlight the desperation and cowardice of those responsible,” Singh said. Television channels showed some people lying on the streets, their clothes soaked in blood. “The impact of the blast was so huge, a packed bus got half burnt and we pulled out a lot of injured people and sent them to hospital,” Pankaj Goswami, a witness at a blast in Guwahati, said. A wave of bomb attacks has hit India in recent months, killing more than 125 people. Police have blamed most of those attacks on Muslim militants, although some Hindu militants have also been suspected of carrying out several attacks. Thursday's blasts “look like the handiwork of terrorist groups from Bangladesh, as you need sophisticated militant groups to carry out such coordinated attacks,” Major General Ashok Mehta, a security analyst, said in New Delhi. “It is quite possible that separatist groups are not involved at all,” Mehta added. President Asif Ali Zardari and Prime Minister Yousuf Raza Gilani of Pakistan, which is often blamed by New Delhi for fomenting trouble in India, condemned the blasts, saying terrorism in all forms needs to be eliminated. The United States Ambassador to India, David C Mulford, deplored the “horrific attacks on innocent people.” Canada also condemned the bombings.