Two people were killed and 11 wounded when a hand grenade exploded in the VIP section of the audience at a concert led by Indian film superstar Shah Rukh Khan and two other actors, police said.

Both the dead were Sri Lankans, police said -- a 21-year old freelance photojournalist and a 25-year-old woman, an employee at the hotel where the Indian stars were staying.

Khan, Bollywood's most popular heartthrob, and other performers were unhurt, Senior Superintendent of Police Sarath Lugoda told Reuters.

Someone threw the grenade as Khan was performing on stage at the tail end of a three-hour show late on Saturday night which had drawn protests from the Indian Ocean island's majority Sinhala Buddhist community.

About 25,000 people attended the sell-out concert at the race course grounds in central Colombo.

"There were close to 1,500 police and military personnel providing security here, we are baffled as to how the attacker smuggled in the grenade," Lugoda said.

One police source said the assailant had attempted to throw the grenade at the stage, where Khan was performing the last act of the show at the time, but that it had fallen short.

The injured were mostly Sri Lankan. But Rithu Shastri, the wife of former Indian cricket captain Ravi Shastri, was among the injured.

There was no word on who could be responsible and police said a full-scale investigation was underway.

A spokesman for the event organizers said Khan was rushed backstage after the blast and was a "bit rattled."

Back in Bombay early on Sunday, Khan -- currently India's most commercially successful star -- told reporters at the airport that he felt the attack was not related to Buddhist protests against the concert.

CLASH WITH POLICE

A few hours before the show began, large crowds of protesters led by Buddhist monk parliamentarians had clashed with riot police near the concert venue.

Police used teargas to disperse the crowds and arrested more than a dozen protesters who wanted the concert postponed as it coincided with the anniversary of the death of a widely respected member of the Buddhist clergy.

"This has nothing to do with that agitation. It is not related at all. We had paid our homage to the Buddhist messiah who had expired a year back," said Khan, who has strung together a series of hits in recent years, including films in which he played a psychopath and a love-struck alcoholic.

Buddhist monks called off protests after Khan apologized for the timing of the concert and promised to observe a minute's silence at the start of the show in memory of monk Gangodawila Soma who died while on a visit to Moscow last year.

Sri Lanka has also been torn for decades by a separatist rebellion by guerrillas from the Tamil minority. But the Tamil Tigers and the government have largely kept to a cease-fire for almost three years and police ruled out any rebel involvement.

Those at the concert said they were chaotic scenes after the blast.

"We don't know what happened, there was a loud noise and everyone started to run, it was chaos," said crew member Anton Dorgan, who suffered minor shrapnel injuries in the blast.

Another Indian movie star, Saif Ali Khan, who has made waves in the last two years with a string of big hits, said Shah Rukh Khan was near the site of the blast.

"There was a big explosion on stage when Shah Rukh was performing at the end of the show," Saif said at the airport.

"I believe this is a terrorist act."

Indian actress Preity Zinta, known for her bubbly girl-next-door image, also returned with the two Khans to Bombay.