New Delhi: The United States advised its citizens to defer travel to Mumbai for "at least the next 48 to 72 hours" following terrorist attacks that left scores of people dead.

"Americans throughout India should be vigilant about security at all times," the US embassy in New Delhi said in a travel advisory on its website.

Eight foreigners were among those killed in coordinated shootings and explosions across India's financial hub that started late on Wednesday.

Commandos hunted for militants who stormed the luxury Taj Mahal Palace and Tower hotel and the Oberoi Trident complex and took hostages.

Media reports indicate Americans have been targeted, according to the travel advisory.

US citizens living or travelling abroad were urged to register with the nearest embassy or consulate to make it easier to contact them in case of emergency.

All hostages were freed from the Taj late on Thursday and at least 15 people were freed from the Oberoi, police said.