Over one hundred and twenty people have been killed or wounded in an attack by the gunmen in Las Vegas of the United States.

According to the police officials, more than 20 people were killed after gunmen opened fire in Mandalay Bay hotel.

The officials are saying that the attack was apparently carried out by a man, believed to be a local resident, who started shooting spree from the 32nd floor of the hotel.

In the meantime, another police official has told the local media outlets that a man identified as a local resident has been shot and killed by the security forces.

The officials also added that a search operation is underway for another individual who is also believed to be involved in the attack.

On the other hand, a spokeswoman for a hospital has said there are fears that the death toll could rise as at least 14 people have been admitted with critical wounds.

The incident has taken place amid ongoing music festival in the city which kicked off on Friday.

The main motive behind the attack has not been ascertained so far and it is yet not clear if it was an act terrorism or not.