Imphal, Aug 1 (IANS): At least five people were killed Monday when a powerful bomb exploded in a market in this Manipur capital, police said.

"The bomb exploded at a shop in the Sangakpam market in the capital city at around 2 p.m., killing five people on the spot. Twenty people were also injured and admitted to the hospital," a police spokesperson told reporters.

Chief Minister Okram Ibobi Singh, who also holds the home portfolio, visited the spot and ordered an inquiry.

"Casualties may increase as the injuries of some of the people are stated to be critical," the police official said.

The Manipur government had intensified security in Imphal and other sensitive places after rebels hurled grenades at some houses at Chingamathak Manipur College Road near here Sunday.

The grenades did not explode and no one was injured in the attack. All the four targeted houses are located under the Imphal municipality area from where the government recently lifted the controversial Armed Forces (Special Powers) Act.

Police suspect that separatist outfits might step up violence in this volatile northeastern state ahead of Independence Day.