At least 20 people were killed and 80
injured as serial blasts ripped through three busy market areas in New Delhi on Saturday, officials and news reports said.
Police said five blasts took place in the city's crowded Ghaffar Market, Connaught Place and Greater Kailash areas within 40 minutes beginning at 6:15 pm (1245 GMT).
Delhi police chief YS Dadwal said a majority of the casualties were reported from Ghaffar Market and Connaught Place.
According to the PTI news agency, 16 people were killed in the Ghaffar Market explosion and four lives were lost in Connaught Place.
Confirming that the deaths were the result of a terrorist attack, Federal Home Minister Shivraj Patil said, "People should maintain calm, social harmony and understanding."
"Let us jointly fight the tragedy," Patil said, vowing that the culprits would be severely dealt with under the law.
The blasts took place in busy areas that were crowded with weekend shoppers, and doctors treating the wounded at hospitals said the death toll could rise as some of the 80 injured were in a critical condition.
Muslim militant group Indian Mujahideen claimed responsibility for the attacks.
The same group - which Indian police believe to be a front for the banned Students Islamic Movement of India - had also claimed responsibility for serial bombings in May and July in the cities of Jaipur and Ahmedabad, where 119 lives were lost.
The first explosion rocked the Ghaffar market, which was bustling with shoppers. Some witnesses said that the explosive was planted in an auto-rickshaw.
Roshan Lal, a witness at Ghaffar Market, told IANS news agency, "The auto rickshaw was lifted into the air by the impact of the blast, and I saw bodies flying in every direction."
This was followed by two blasts in Connaught Place, at a central park and near a metro station, and another two in the Greater Kailash market area.
The explosives were planted in dustbins in the Connaught Place area, while in Greater Kailash one was in a dustbin and another on a bicycle.
The blast sites were splattered with blood as several injured lay writhing in pain amid damaged vehicles and shops.
Siren-blaring ambulances took the wounded to hospitals.
The NDTV network reported that three unexploded bombs were defused in the India Gate area - one of the highest security zones in the country - and Connaught Place.
Police said initial investigations showed that the explosions were of a low intensity, and ammonium nitrate and shrapnel were used in the explosives that were set off with timers.
According to the Delhi police, two men were detained in the Connaught Place area soon after the blasts, and an e-mail sent by the terrorist group was traced to the suburbs of Mumbai.
"We have vital clues and are hopeful of solving the case very soon," Delhi police spokesman Rajan Bhagat said in response to news reports that said that the investigators had made their first arrest in the case.
Indian Prime Minister Manmohan Singh held an emergency cabinet meeting as the entire country was put on heightened security alert.
Junior Home Minister Sriprakash Jaiswal admitted an intelligence failure on the part of the authorities.
"The terrorists managed to fool us and get away this time," Jaiswal told the IANS, speaking of involvement of "external forces" in the blasts.
Indian security agencies have often blamed Pakistan-based militant groups of masterminding attacks in the country with help from local Muslim groups.
Pakistani President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani strongly condemned Saturday's blasts, expressing their shock and grief over "the loss of precious human lives," according to the state-run Associated Press of Pakistan.
"The elements involved in such heinous act are enemies of humanity," Gilani said.
The US also condemned the terrorist attacks and extended sympathies to the families of the victims.
"There is no justification for the vicious murder of innocent people," US envoy to India David Mulford said in a statement. "The US stands shoulder to shoulder with India in the fight against terror."
India is among the countries worst affected by terrorism. More than 650 people have been killed in terrorist attacks in Indian cities over the past eight years.
The deadliest terrorist attack in recent years was in July 2006, when multiple bombings hit Mumbai's train network, killing 180 people, dpa reported.