A one-year-old girl has been killed and at least 34 people have been injured by a bomb explosion in the northern Indian holy city of Varanasi, officials say.
The small, improvised device was hidden in a milk canister at a bathing point on the banks of the River Ganges near the Vishwanath temple, police said.
The injured included Hindu worshippers attending an evening prayer ceremony.
Police said the blast appeared to be a terrorist attack and that officers had been placed on high alert nationwide.
The authorities have also ordered other sensitive sites in Varanasi to be searched thoroughly.
The explosion occurred at about 1830 (1300 GMT), and struck those attending the Ganga aarti prayer ceremony at the Shitla ghat - one of the many stone staircases which lead down to the Ganges.
The United News of India news agency said the powerful explosion shook nearby buildings and knocked over iron railings around the Vishwanath temple. Stone walls up to 60m (200ft) away were damaged.
One witness told India TV that some people were hit by metal shrapnel. Blood-soaked debris was left scattered along the embankment.
District officials in Varanasi told the BBC that the injured included two Italian nationals - a man and a woman.
Senior police official Brij Lal earlier said the girl who died had been sitting on her mother's lap when the bomb went off. He added that her mother and two others were in serious condition in hospital.
Some of the injured were hurt when railings collapsed as people tried to get away from the scene, officials said.
Prime Minister Manmohan Singh has appealed for calm.
"The blast is an attempt to weaken our resolve by the evil forces of terrorism. In this, the terrorists will not succeed," he told reporters in Delhi.
One of Varanasi's MPs, Murli Manohar Joshi, meanwhile accused security forces of not being alert to the threat.
"This is a clear-cut indication that terrorist outfits in [Uttar Pradesh] are once again active," he told the Times Now TV channel. "It appears as if the police have also been lax."
The BBC's Chris Morris in Delhi says the only good news for the authorities is that the device used in Tuesday's incident - although deadly - was not particularly powerful.
History of violence
An Islamist militant group, the Indian Mujahideen, has sent an email saying it was behind the explosion.
It speaks of revenge for the destruction by Hindu extremists on 6 December 1992 of the 16th Century Babri mosque in the northern Uttar Pradesh town of Ayodhya.
It also criticises a verdict by the high court in Lucknow that split the disputed land where the mosque used to stand between a Muslim group and two Hindu groups, and said it should not be rebuilt there.
The authorities are working to verify the authenticity of the message. The Press Trust of India reported that the email was sent from a computer in a suburb of Mumbai, and that police had been sent to the area.
Varanasi is the religious capital of Hinduism and is usually packed with Indian pilgrims and foreign tourists.
Hindus believe that if a person is cremated in Varanasi, or the ashes of the dead are scattered in the river and last rites offered, the deceased will achieve release from sufferings of the cycle of birth and death.
The Ganga aarti, which takes place daily at sunrise and sunset on the Shitla, Dashashwamedh and Prayag ghats, is attended by 2,000 to 3,000 people, many of whom are foreigners.
Also known as Benares, the city - about 670km (415 miles) south-east of the capital, Delhi - has a history of religious violence.
In 2006, 15 people were killed and dozens injured when bombs exploded at the Sankot Mochan temple and the main railway station.