Uttar Pradesh police on Friday announced a reward of Rs 1 lakh to anyone providing a concrete lead to those behind the twin blasts in Varanasi on Tuesday that left 20 dead and over 50 injured.

"The identity of the person providing information and helping the police arrest those responsible for the blasts would be kept secret," Director-General of Police Yashpal Singh told reporters in Varanasi.

He said the name of a shopkeeper had come up during investigations from whom the terrorists had purchased the pressure cookers to carry out the explosions.

"Efforts are under way to locate the shop," he said, admitting that no concrete lead had been found so far. He, however, was confident that the case will be solved within a week just like the terrorist attack in Ayodhya (July 5 last year) was solved by the Special Task Force of UP police in seven days' time.

There was information on Salar, the Lashkar-e-Tayiba terrorist shot dead by the STF in Lucknow on Wednesday, being involved in the terrorist strike and police were investigating what he was doing in Varanasi on the day of the blasts, he said.