At least four people have been killed and 18 injured in a mass shooting in Birmingham, Alabama, police say.

“Multiple shooters fired multiple shots on a group of people” late on Saturday in the Five Points South area of the city, Birmingham Police officer Truman Fitzgerald said.

Officers found the bodies of two men and one woman at the scene, while a third man later died of bullet wounds in hospital, Birmingham Police said

The culprits are believed to have approached the scene in a vehicle before getting out and opening fire. No suspects have been arrested.

Mr Fitzgerald added that they believed the shooting was “not random and stemmed from an isolated incident where multiple victims were caught in the crossfire”.

The shooting may have been a result of a murder-for-hire plot, Police Chief Scott Thurmond was quoted as saying by local news outlet Al.com.

The intended target was among those killed, Mr Thurmond said at a news conference on Sunday.

“It wasn’t the location, it was the person, so wherever the person was was where it was going to take place, wherever they can catch that individual,’’ Mr Thurmond said. "That’s just where they happened to catch them.”

The other victims - all of whom were standing outside - are so far believed to have been caught in the gunfire.

Four of the injured suffered life-threatening wounds, according to Mr Fitzgerald.

The BBC has contacted the Birmingham Police Department for comment.

Authorities are also pressing to find the shooters.