Indian police combed the sites of three powerful blasts in New Delhi on Sunday for clues to who carried out coordinated attacks that killed at least 57 people, just days before major Muslim and Hindu festivals.

Prime Minister Manmohan Singh, who cut short a visit to Kolkata to rush back to the capital, blamed Saturday night's attacks in crowded pre-holiday bazaars on terrorists, but said it was too early to speculate who was behind the blasts.

New Delhi's chief minister appealed for people to stay away from public areas for the next few days ahead of the major Hindu celebration of Diwali, or the festival of lights, on Tuesday and the Islamic Eid al-Fitr a few days later.

In Delhi, extra armed police manned new barricades on the streets and the turnout at some temples and mosques was lower than normal in the cool, clear autumn morning.

"There is some sense of fear, obviously," said 40-year-old Mohammad Salim.

The financial capital of Mumbai, hit by major bombings in 2003 and 1993, and other cities were on alert and security was stepped up at airports and rail and bus stations across India.

S. Regunathan, the top bureaucrat in Delhi's local government, told Reuters that 57 people were killed and about 140 wounded in the blasts.

More than 110 were still in hospital, many of them critically injured, some with severe burns. Some local media put the death toll as high as 70.

Media said 10 people had been held for questioning, but this was not confirmed by police. Many of the dead have yet to be identified and anguished relatives waited outside major hospitals through the night.

Appeal for calm

The blasts struck two markets and near a bus at another as dusk fell across the capital of 14 million people, a time when bazaars were packed with people shopping for special sweets and last minute presents for the coming festivals.

India has blamed previous attacks on Pakistan-based armed groups, including one on parliament in 2001 that brought the two countries close to war over Kashmir.

But the country is also racked by scores of revolts and in May two blasts blamed on Sikh separatists killed one person and wounded dozens in Delhi.

Monday also marks the 21st anniversary of the assassination of then Prime Minister Indira Gandhi by her two Sikh bodyguards.

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