As another victim succumbed to his injuries from Saturday's coordinated explosions, bringing the death toll to 62, investigators said they hoped mobile phone records could lead to a breakthrough in the case.

The city overnight brought in 2,600 security personnel to bolster New Delhi's 71,000-member police force and invited out-of-town forensic experts to help speed up investigations, a senior police official said.

"We are using all our resources, which includes spotters, informers and even known hoodlums, to crack this case as early as possible," she told AFP.

Three nearly simultaneous blasts tore through a bus and two crowded markets on Saturday in an attack claimed by the Islamic Revolutionary Group, believed to have ties to a leading militant group fighting Indian rule in Kashmir.

The carnage cast a pall on the capital ahead of Tuesday's holiday of Diwali, the festival of lights. Some markets were emptier than usual as nervous residents stayed away after the blasts, which also injured 210 people.

A police commissioner who asked not to be named said detectives were sifting through millions of mobile telephone call records, trying to uncover who carried out the attacks.

"We are going through calls originating from 18 cellular towers at the three blast sites because we believe the attacks were coordinated with the help of mobile phones," the commissioner said.

"It's hard work but at the end we will get what we want," he said.

Police guarded Delhi's 18 exit points and prowled airports, rail and inter-city bus stations for suspects in what a police spokesman said was one of the biggest ever manhunts in the capital.