Duane "Keffe D" Davis was arrested early on Friday morning, according to the Associated Press (AP), who cited two unnamed officials with first-hand knowledge of the arrest.

However, the exact charge or charges were not immediately clear, with a formal indictment expected later on Friday, according to AP.

The arrest represents a long-awaited break in a case that has frustrated investigators and fascinated the public ever since the hip-hop star was killed on the Las Vegas Strip 27 years ago.

Born in New York City, Tupac became one of the leading figures in the West Coast hip-hop scene, with hits including "California Love" and "Dear Mama".

Known by his stage name 2Pac, he was nominated for a Grammy Award six times and is widely considered to be one of the most influential rappers of all time.

He was killed on the night of 7 September 1996, while in a black BMW driven by Death Row Records founder Marion "Suge" Knight.

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They were waiting in a convoy of about 10 cars at a red light, a block from the Las Vegas Strip, when a white Cadillac pulled up next to them and gunfire erupted.

Tupac died after being shot multiple times. He was 25 at the time.

The shooting unfolded shortly after a casino brawl earlier in the evening between Orlando Anderson, Tupac and their associates.

There were many witnesses, but the investigation quickly stalled, in part because those witnesses refused to cooperate, Las Vegas police said in the past.

There have never been any arrests, yet attention on the case has endured for decades.

The man arrested on Friday, Mr Davis, is the uncle of Mr Anderson - one of Tupac's known rivals who authorities have long suspected in the rapper's death.

Mr Anderson denied any involvement in Shakur's killing at the time, and died two years later in an unrelated gang shooting.

In July, police searched a property which public records, including voting records, linked to the wife of Mr Davis.

At the time, police confirmed officers had served a search warrant in Henderson, a city near Las Vegas.

However, the department did not release any other details, including where officers were searching and whether they expect to make an arrest.