At least 15 people have been killed in twin bomb explosions in the northern Indian pilgrimage city of Varanasi.
The temple was packed at the time of the blast
At least 60 others were injured, police said. The first blast occurred at a Hindu temple and was followed by another at the main railway station.
Police also said they defused two more bombs in the city. No-one has so far said they were behind the attacks.
Varanasi is the religious capital of Hinduism and is usually packed with Indian pilgrims and foreign tourists.
Indian Prime Minister Manmohan Singh condemned the blasts and appealed for calm.
The city in the state of Uttar Pradesh, about 670km (415 miles) south-east of the capital Delhi, has a history of religious violence.
The first explosion took place in the major Sankot Mochan temple dedicated to the Hindu God Hanuman at about 1815 local time (1245 GMT).
At least 10 people were killed and a number of others injured in the blast, Uttar Pradesh officials said.
An eyewitness, Siddharth Suri, told the BBC that thousands of people were at the temple at the time of the blast.
Tuesday is a special day at the Sankat Mochan temple and the explosion took place just minutes before the main worship.
"There was a loud explosion followed by dust. There was pandemonium in the front of the temple," Mr Suri said.
"The explosion at the temple is horrific and shocking to me," high priest of the temple Veer Bhadra Mishra told the BBC News website.
"The Sankat Mochan temple is loved, respected and revered by so many people as a place of religious worship and ritual. I am so pained," the priest said.
The complex would have been packed with worshippers and the fear is the explosion was timed to have maximum impact, the BBC's Nadvip Dhariwal in Delhi reports.
Minutes later, the city's main railway station was rocked by another blast, with eyewitnesses saying they saw a number of casualties.
The blasts occurred very near the entrance to the station, close to a tourist information counter, one eyewitness told the BBC News website.
Officials said experts also defused two bombs - on the bank of the River Ganges and at a city market. One of the bombs had a timing device.
Police secured the sites of the blasts, and security was stepped up throughout the city.
"The blasts were pretty big and I do not rule out a terrorist hand behind it," Varanasi's police chief Navneet Sikera was quoted as saying by Reuters news agency.
Major cities across India, including the capital, Delhi, were put on high alert, following the explosions.
India's cabinet committee on security, meanwhile, held an emergency meeting.
Do you live in the area? Have you been affected by the incident?
It is not an attack on any temple but a well planned and strategised doing of terrorists trying to play with the communal harmony of one of the oldest city of world. But it's for sure that people here are quite aware of these tactics and should not fall in these cheap doings. I see a more united and cooperative behaviour from the citizens of the holy city Varanasi.
Upendra Gupta, Varanasi, India
We live in BHU, approx 2kms aerial distance from the site of the blast, the Sankat Mochan Temple, but we felt the shocks and a loud sound of the blast. Selection of a Hindu temple as a bomb site, that too on a Tuesday, can trigger off a chain reaction of riots in the city which can further hamper the image of India. This concern was shown by the local administration and soon whole city was put on high alert and a light curfew was put up in the sensitive areas. The air is calm now but the hearts are not.
Surya, Banaras Hindu University, Varanasi, India
I just went to Varanasi to see the beautiful temples there. It was very crowded with lot of devotees coming specially to pray on Tuesday. As soon as the blast occurred everyone were seen running. People was terrified but did not get into any blame game and I am sure peace will prevail and it will not lead to another communal riots in India.
Tom Jose, Mumbai, India
I was born and brought up in Varanasi. My parents still live there and they go to Sankat Mochan daily. My Mother was there two hours before the attack. And my best friend was actually in the temple when the blast took place. Fortunately she is safe. But the very thought that I could have lost her sends shivers down the spine. Still I don't blame people from any particular religion for what happened. And I appeal to all the people in India specially Varanasi to maintain calm. Terrorists don't belong to any religion.
Suruchi Pandey, Bristol, UK
I was near the temple, actually going there. People say quite a lot of children have been injured, but still it is not clear. I was nearby, on my way to the temple. In the area all the shops are closing because people started to run throwing stones. The area is now blocked. I'm an Italian journalist, in Benares by chance.
I was going out to run few errands. I saw the traffic halted and people running around. Lots of police vehicle and ambulances. People are really angry with the incident. The city border is sealed, shops are closed and security measures are being taken. Another bomb blast on the railway station. It has shaken up the city.
Kripal Singh, Varanasi, India
The temple is one of the most important in the holiest city of the Hindus. Tuesday is the busiest day at the temple. The blasts were calculated to create the greatest loss of human life while devotees were offering prayers.
Tito Basu, Tampa, Florida, USA
Varanasi is not just a Holy Temple Town but is what Mecca is to Muslims and Vatican to Catholics. This could result in riots throughout the country. Varanasi also happens to be what can be called the oldest living city in the world. The city finds mention in epic Mahabharath. The Queen of Hastinavathi (somewhere near Delhi) was the daughter of King of Kashi (Varanasi)
Raghavendra S Kattinakere, Bangalore
We go to the temple for peace not for blast, it hurt and triggers the feeling. Even now I pray to God for peace not for revenge of the terrorist.