Cities across India are on high alert, a day after twin bomb blasts rocked the holy city of Varanasi.
Fourteen people are confirmed dead in the blasts at a Hindu temple and a railway station and 105 were injured, state officials told the BBC.
Some reports put the death toll at more than 20 but this cannot be confirmed.
The government says its main concern is to stop religious violence flaring up. Uttar Pradesh state has a history of clashes between Hindus and Muslims.
Local religious leaders have joined Indian Prime Minister Manmohan Singh in appealing for calm.
Home Minister Shivraj Patil and the head of the governing Congress Party, Sonia Gandhi, went to Varanasi and visited the scene of the attacks.
Security has been stepped up around the areas that were bombed and in major cities, including the capital, Delhi.
No group has so far said it was behind the attacks.
The BBC's Mark Dummett in Varanasi says a wedding party took the brunt of the blast at the Sankat Mochan temple.
He says shoes of devotees lie scattered on the ground, which is stained with blood. Flies are everywhere.
Some Hindu groups called for a strike in Varanasi in protest against the attacks.
Despite the call, some shops were open and vehicles on the roads. Trains ran as normal and morning prayers were held in the many temples dotting the city.
Varanasi, also known as Benares, is about 670km (415 miles) south-east of Delhi.
It is the religious capital of Hinduism and is usually packed with Indian pilgrims and foreign tourists.
The twin blasts both occurred at about the same time, 1815 local time (1245 GMT), witnesses told the BBC News website.
The first took place in the Sankot Mochan temple dedicated to the Hindu God Hanuman, shortly before Tuesday's main evening prayer was to begin.
Minutes later, the main railway station was rocked by a second blast. State Home Secretary Alok Sinha told the BBC nine people had died in the temple blast, and five in the explosion at the railway station.
Mr Patil told reporters it appeared explosives had been placed in a pressure cooker in the temple attack.
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.
The explosions happened days after Hindus and Muslims fought one another in the nearby city of Lucknow.
"The explosion at the temple is horrific and shocking to me," the 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."
In a separate incident, police in the state capital, Lucknow, say they killed a militant wanted in connection with last October's bomb blasts in Delhi in which more than 60 people were killed and 210 injured.
They say the dead man was a member of the Lashkar-e-Toiba, a militant group fighting Indian rule in Kashmir.
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