A day after India's financial capital, Bombay, was hit by a series of powerful explosions on commuter trains, Indian Prime Minister Manmohan Singh urged the country to stand united in the face of terrorism.

In a nationally televised address, Prime Minister Manmohan Singh said India will not be beaten by terrorism.

"No one can make India kneel," he said. "No one can come in the path of our progress. The wheels of our economy will move on. India will continue to walk tall and with confidence. Let me assure you, the government will do whatever is required to deal with the challenge at hand."

The prime minister praised the courage with which the city had resumed normal life after the blasts.

In Bombay, police said it was too early to say who might have been responsible for the powerful bomb blasts that killed hundreds of commuters.

Maharashtra State Police Director-General P.S. Pasricha said explosives and weapons seized in recent months had indicated that the thriving financial capital was a potential terrorist target.

"The country is on the path to progress, so naturally some anti-national elements would not be very comfortable with that," said Pasricha. "They would like to play that kind of mischief to see that our progress is hampered, and the fear psychosis is created to stop investments."

Pasricha said the coordinated explosions were in the style of Lashkar-e-Taiba, a Muslim militant group active in Indian Kashmir. The group has been blamed in the past for carrying out near-simultaneous explosions in cities including the capital, New Delhi.

But Lashkar-e-Taiba and another Kashmiri Islamist group, the Hizb-ul-Mujhaideen, strongly denied any role in Tuesday's blasts.

The scars of the bombings are evident everywhere in Bombay. Overwhelmed hospitals struggled to cope with the hundreds of injured. Many of Bombay's 16 million inhabitants, who include the country's richest people and residents of Asia's largest slums - spent the day hunting for missing relatives.

Local television stations ran pictures of missing people and messages from loved ones.

But Bombay did not remain in the grip of fear for long. Less than 24 hours after the bombs stunned the city, schools and colleges opened. Services were restored on the suburban rail network, and many commuters rode on the trains despite apprehensions.

Stock markets rose by nearly three percent, calming fears that investor confidence in India's rising economy had been undermined by the blasts.

Bombay is India's commercial nerve center, home to many corporate headquarters and a thriving movie industry. India wants to make the city an Asian financial hub.