By Friday afternoon, gunfire and explosions continued to erupt from the luxury Taj Mahal Hotel as a lone militant fought on, but commandos said they had finally gained control of the nearby five-star Trident-Oberoi after killing two of the attackers.
The crack Indian troops seemed to grant their foes a grudging respect for their military know-how and planning.
'These people were very, very familiar with the hotel layout and it appeared they had carried out a survey before,' the chief of the elite Naval Commando Unit, his face covered with a black scarf and sunglasses, told reporters.
'A very determined lot, remorseless,' he said, adding that he had seen around 50 bodies scattered through the Taj hotel, including at least 12 in a single room.
The attackers were young men under the age of 30, carrying AK-47 assault rifles and grenades, obviously trained in how to use them.
'They were moving from one place to the other,' the masked commando said, adding there were three to four of them raining fire and grenades on the commandos.
On Thursday night, the head of the elite National Security Guards said just one militant was left at the Taj, adding that he was wounded and would be 'mopped up' soon.
But on Friday, it was apparent the lone gunman was proving a hard nut to crack, as explosions and gunfire erupted first from one floor and then another.
'He is moving in two floors, there is a dance floor area where apparently he has cut off all the lights. And sometimes he gets holed up into some of the rooms, and he has made the area dark,' Lieutenant-General N. Thamburaj told reporters.
'This morning while carrying out the operation we heard the sound of a lady and a gentleman, so it is possible that this terrorist has got two or more hostages with him,' he added.
The attackers' determination has been matched only by their ruthlessness. On Wednesday, some walked into the city's main railway station and fired indiscriminately on the crowd, killing 47 people in the blink of an eye.
Guests who escaped the hotel told of bodies littered in the corridors, although one Briton said the attackers had released some women hostages when they started to panic in the early stages of the siege.
Naval commandos said they had recovered a Mauritian national identity card, seven credit cards, and more than US$2,000 (S$3,018) in and Indian rupees in the Taj hotel.
They also found grenades, ammunition, dried fruits and almonds - signs, they said, that the attackers had been prepared to sustain themselves during a long siege.
'We are not aware how many have been killed,' the masked commando said of the battle at the Taj.
'When exchange of fire takes place in darkness and there is blood all over, there are bodies lying all over,' he said.
'You are not looking at who is injured and who is killed, you are just looking at somebody who has weapons on him.' -- REUTERS