Law enforcement officers were targeted in attacks in cities across the country overnight, with some officers wounded in gun battles in St Louis and Las Vegas and others injured as they were run over by cars in New York City and Buffalo.

An officer was in critical condition on Tuesday after being shot down near the Circus Circus Hotel and Casino in Las Vegas as the police tried to disperse crowds that were pelting them with bottles and rocks, officials said.

In an unrelated episode, a person carrying several firearms was killed after he opened fire on police forces guarding a federal building on Las Vegas Boulevard, according to the authorities.

“This is a sad night for the LVMPD family and a tragic night for our community,” Sheriff Joseph Lombardo said of the Las Vegas Metropolitan Police Department at a news conference in the early hours of Tuesday. The officer was transported to the University Medical Center and is on life support, he added, and a suspect was taken into custody.

“With these protests which are leading to riot,” he said, “one tragedy is only leading to another”.

In St. Louis, four officers were struck by gunfire in a shootout between gunmen at a protest and the police. The officers’ injuries were believed to be “non-life threatening”, Chief John Hayden of the St Louis Police Department said at a news conference.

Chief Hayden said that after a peaceful protest of a few thousand people, a smaller group had broken off, intent on causing mayhem. Some in the crowd were armed and “flourishing pistols”, the chief said. Two officers were shot in the leg, one in the foot and one in the arm, he said.

Elsewhere, police officers were intentionally struck by vehicles.

A New York officer was run over by a black sedan at 12.45am on Tuesday in the Bronx, according to a police spokesman. The officer was in stable condition on Tuesday, the police said.

That episode followed an attack on Monday in Buffalo, New York, when the driver of an SUV sped through a line of law enforcement officers in riot gear, injuring two of them in an episode that was caught on video.