At least 25 rebels attacked a cultural festival in the state of Jharkhand early on Saturday, firing on the crowd, India's Press Trust news agency said.

The son of ex-chief minister Babu Lal Marandi was attending the event.

The border with the neighbouring state of Bihar was sealed to prevent the rebels fleeing, police superintendent Arun Kumar Singh told the AFP agency.

The cultural festival followed a football match that was played on Friday afternoon.

Serious threat

"The police security personnel deployed left the place after the football match," Mr Singh told AFP. "They did wrong. They should have stayed."

Another four people were reported to have been injured in the attack.

Maoist rebels operate in 182 districts in India, mainly in the states of Jharkhand, Bihar, Andhra Pradesh, Chhattisgarh, Madhya Pradesh, Maharashtra and West Bengal.

Prime Minister Manmohan Singh has said the Maoists pose the most serious threat to national security in India.

More than 6,000 people have died during the rebels' decades-long fight for a communist state in parts of India.