Police have released two new images of a suspect in the hunt for the gunman who killed a health insurance chief executive in New York.

UnitedHealthcare boss Brian Thompson, 50, was shot in the back as he made his way to a conference on Wednesday, in what police believe was a targeted attack.

On Saturday, city mayor Eric Adams said the "net is tightening" around the gunman, who has so far evaded police despite an extensive search and the use of facial recognition technology.

The FBI has offered a $50,000 (£39,000) reward for information leading to the suspect's arrest.

The latest images of the man being sought are both taken from a vehicle. In one, he can be seen in the back of a taxi wearing a hooded sweatshirt and a disposable face covering.

In the second, he is seen outside of the car, again wearing a facemask.

The new appeal came as US media reported a backpack thought to belong to the suspect recovered near the scene contained a Tommy Hilfiger jacket and paper money from the board game Monopoly.

Thompson, a 50-year-old father of two, was shot as he made his was to an investor conference in Midtown Manhattan where he had been scheduled to speak later that day.

Police said the gunman first fled the scene on foot, before riding a bike towards Central Park.

The motive for the killing is still being investigated. Authorities have confirmed the words "deny", "defend" and "depose" were written on the bullet casings found close to the victim's body - language which could be associated with critics of the US's private health insurance industry.

On Friday, a person familiar with the matter told CBS News, the BBC's US partner, that investigators believed the suspect was no longer in New York City and may have boarded a bus to the city of Atlanta in the state of Georgia.