At least 78 people were killed and 200 injured today when gunmen opened fire on a crowded Mumbai railway station, luxury hotels and a restaurant popular with tourists.
Johnny Joseph, chief secretary for Maharashtra state in India, of which Mumbai is the capital, says the death toll could rise further.
The gunmen attacked the Chhatrapati Shivaji Terminus station in southern Mumbai and Leopold's restaurant, a Mumbai landmark, along with the Oberoi and Taj Mahal hotels.
The motive for the attacks was not immediately clear but Mumbai has frequently been targeted in terror attacks, often blamed on Muslim militants, including a series of blasts in July last year that killed 187 people.
Several European MEPs were among those barricaded inside the Taj, a century-old seaside hotel complex and one of the city's best-known destinations.
Sajjad Karim, part of a delegation of MEPs visiting Mumbai ahead of a forthcoming EU-India summit, said: "I was in the main lobby and there was all of a sudden a lot of firing outside."
He turned to get away "and all of a sudden another gunman appeared in front of us, carrying machine gun-type weapons. And he just started firing at us ... I just turned and ran in the opposite direction," he said.
Hours later, he remained holed up in the hotel, unsure if the incident was over, and whether it was safe to come out.
"We have no idea what's going on," he said.
Arvind Kodekar was at a wedding reception at the Taj Mahal when an explosion rang out.
He said: "When we heard the sound of the blast, everyone - the bride, the groom, everyone - just ran. We heard the sound of two blasts and we just ran."
At the Oberoi, police officer P.I. Patil said shots were fired inside and the hotel had been cordoned off.
Mumbai General Railway Police Commissioner A.K. Sharma said several men armed with rifles and grenades were holed up in the railway station.
Leopold's restaurant was riddled with bullet holes and there were blood stains on the floor and shoes left by fleeing customers.
The Taj Mahal Palace, one of the most famous hotels in India, was home to the England cricket team when they visited Mumbai around two weeks ago.
They were also planning to use the hotel on their return to the city for the team's second Test Match against India, which is scheduled to start on 19 December.
The team were in the eastern Indian city of Cuttack today after losing their latest one-day game against India.
India has been wracked by deadly bomb attacks in recent years, which police blame on Muslim militants intent on destabilising the largely Hindu country.
Since October 2005, nearly 700 people have died in the bombings. And since May a militant group calling itself the Indian Mujahideen has taken credit for a string of blasts that have killed more than 130.
The most recent was in September when a series of explosions struck a park and crowded shopping areas in the capital, New Delhi, killing 21 people and wounding about 100 others.
Mumbai has been hit repeatedly by terror attacks since March 1993, when Muslim underworld figures tied to Pakistani militants allegedly carried out a series of bombings on Mumbai's stock exchange, trains, hotels and petrol stations.
Authorities said those attacks, which killed 257 people and wounded more than 1,100, were carried out to avenge the deaths of hundreds of Muslims in religious riots which swept India.
Ten years later, in 2003, 52 people were killed in Mumbai bombings blamed on Muslim militants and in July last year a series of seven blasts ripped through railway trains and commuter stations. At least 187 died in those attacks.
Relations between Hindus, who make up more than 80% of India's population, and Muslims, who make up about 14%, have been relatively peaceful since British-ruled India was split into independent India and Pakistan in 1947, but there have been sporadic bouts of violence.