One person was killed and 11 others critically injured as two motorcycle-borne gunmen went on a rampage in Bihar's Begusarai district, firing indiscriminately at people in crowded areas, police said.

The assailants are yet to be identified, they said.

The gunmen opened fire at Malhipur Chowk in Begusarai town on Tuesday evening, targeting shops in the busy area, a police officer said.

Panicked people started running for their lives, while shopkeepers fled leaving shops open.

The miscreants then went to Barauni Thermal Chowk, Barauni, Teghra, Bachwara and Rajendra Bridge, and continued firing at people, he said.

A 30-year-old man, Chandan Kumar, was killed and 11 others were critically injured in the mayhem, Superintendent of Police Yogendra Kumar told reporters.

Some of the injured were admitted to the government hospital in Begusarai, while others were sent to Patna for better treatment, he said.

Security has been beefed up in the district, and all the entry points have been barricaded after the incident.

"Investigation is underway. We will soon nab the accused," the SP added.