A Mumbai Police team on Monday visited Bollywood actor Salman Khan's residence in suburban Bandra and heightened security around the premises, a day after the actor and his father Salim Khan received an anonymous letter threatening to kill them, an official said.

On Sunday morning, noted writer Salim Khan was sitting on a bench at the Bandra Bandstand after a morning walk when an unidentified man kept there a letter which mentioned a threat to kill him and his actor-son.

Later, with the help of his security personnel, Salim Khan contacted the police and an FIR was registered under section 506-II (criminal intimidation) of the Indian Penal Code at the Bandra police station.

On Monday, five officials of the Mumbai crime branch along with local police personnel visited Salman Khan's residence at the Galaxy Apartments in Bandra area and spoke to his family members.

They spent about an hour at the actor's home and then left, an official said.

The police also visited the spot where Salim Khan had got the threat letter, he said.

Taking serious cognisance of the letter, the police are scanning the footage of various CCTVs installed in the area to identity the person who had left the threat note on the bench there, the official said.

Mumbai Police Commissioner Sanjay Pandey said they have taken the threat letter received by Salman "seriously", and all angles of the case will be probed. Earlier in the day, a police team visited Khan's residence in suburban Bandra and increased security around the premises, a day after the actor and his father and screenplay writer Salim Khan received an anonymous letter threatening to kill them.

Talking to reporters, Pandey said, As the matter is serious, so we have also taken this issue seriously. Our officials are actively investigating the case. No one has been detained till now.

"It's too early to say if the letter is fake, and also we can't say anything about the (involvement of) Lawrence Bishnoi gang. But whatever content is there in the letter, we are taking it seriously and conducting probe," the commissioner added.