Gorakhpur was rocked by three bomb blasts on Tuesday evening. Although there were no casualties, five persons were injured.
All three blasts occurred within 15 minutes of one another at Gol Ghar market, the city's commercial hub. The injured have been admitted to hospital.
As panic gripped the area, security was tightened in and around the blast sites.
The bombs were concealed in lunch boxes stored in three separate bicycles. The first one went off near Baldeva Plaza petrol pump at 7.15 pm, police sources said. The second bomb exploded at 7.20 pm near a transformer close to a waterworks building, and the third five minutes later near Ganesh Crossing.
Senior police and civic officials, and an anti-bomb squad have rushed to the blast sites. The possible use of a timer device could not be ruled out, police sources said.
In New Delhi, a home ministry spokesman said the state government had been advised to ensure peace in the area. Home ministry officials, including Home Secretary Madhukar Gupta, were in touch with the state government to monitor the situation, sources in the ministry said.
In Lucknow, Principal Secretary (Home) K Chandramauli and Director General of Police GL Sharma reviewed the situation and gave security instructions to the police. A high alert has also been sounded across Uttar Pradesh.
Sharma said that it could either be the handiwork of terrorists or anti-social elements.