The death toll, which is expected to rise, now stands at 121, Mumbai police tell ABC News, among them eight foreigners. There are 279 injured, 22 of whom are foreigners according to the city's police control room.
Eleven of the assailants have been killed and several arrested, as well as 14 policemen, and 327 people were injured, among them three Americans, the Times of India reported, citing the Union Home Ministry.
A previously unknown group that calls itself Deccan Mujahideen has claimed it was behind the attacks, television channels reported on Thursday.
In an email the group allegedly sent to news organizations, Deccan Mujahideen cited attacks on Muslims in India as the reason for the assault.
"You should know that your acts are not at all left unnoticed; rather we are closely keeping an eye on you and just waiting for the right time to execute your bloodshed," the communique said.
The attacks have increased tension between India and Pakistan, which both have nuclear arms. It was "evident" that a "group based outside the country" carried out the attacks, Indian Prime Minister Manmohan Singh said Thursday in an address to the nation.
He didn't elaborate, or name Pakistan, but he said India would "take up strongly with our neighbors that the use of their territory for launching attacks on us will not be tolerated and that there will be a cost if suitable measures are not taken by them."
Indian government sources told ABC News they believe the explosives arrived by boat. Investigators found a rubber boat with explosives in it just 100 feet from the Taj hotel.
The Indian Navy said its forces were boarding a cargo vessel suspected of ties to the attacks. Navy spokesman Capt. Manohar Nambiar said Thursday that the ship, the MV Alpha, had recently come to Mumbai from Karachi, Pakistan.
Pakistan's foreign minister, Shah Mehmood Qureshi, in New Delhi for peace talks, told the Dawn television station that nobody should be blamed until investigations were complete, AFP reported.
"Our experience in the past tells us that we should not jump to conclusions," Qureshi said.
Pakistan's Port and Shipping Minister Nabil Gabol said Indian authorities had not asked him for information about what he called a "false allegation" regarding the origin of the cargo ship suspected of transporting the militants.
British Foreign Minister, David Miliband, also urged caution in apportioning blame, "This is a rapidly evolving situation in which the facts are not yet clear," he told reporters.
The gunmen came prepared for a siege, officials said, even hauling in large bags of almonds to feed themselves during a long gunbattle.
"They have AK-47s and grenades. They have bags full of grenades and have come fully prepared," said Maj. Gen. R.K. Hooda. Vice-Admiral J.S. Bedi, a top naval officer.
Ratan Tata, who runs the company that owns the Taj Mahal, said they appeared to have scouted their targets in advance.
"They seem to know their way around the back office, the kitchen. There has been a considerable amount of detailed planning," he told a news conference.
Survivors told of chaos inside the hotels with the attacks erupting as many sat down to meals in the hotels' dining rooms. They described dead bodies in hallways, by the pool, of hiding behind tables covered with table cloths, of marble and sleek wooden floors streaked with blood.