An unprovoked stabbing rampage on the Las Vegas Strip left two people dead and six others hurt on Thursday, police in the US city said.

Locals and tourists were caught up in the attack, which happened in the middle of the day in a spot usually thronged with visitors.

James LaRochelle of the Las Vegas Metropolitan Police Department said the attacker had used a large knife with a long blade, and apparently attacked his first victim without warning.

"The initial stabbing occurs on the sidewalk area and appears unprovoked," he told a press conference.

The knifeman then ran along the street, attacking several other people.

"Two of which are now deceased, three are in a critical condition. The other victims are at the hospital," LaRochelle said.

Members of the public gave chase as the attacker fled, until he was intercepted by a security guard and police officers, according to LaRochelle.

The suspect, who was described as a Hispanic man in his 30s, is not thought to be local to Las Vegas, police said.

Local television broadcast footage of first responders helping victims in the streets.

Parts of the Las Vegas strip, home to major venues including the resorts Wynn Las Vegas and The Venetian, remained closed on Thursday as detectives scoured the crime scene.

Mass stabbings do not often make the news in the United States, where the scourge of gun crime regularly claims multiple lives.

Thursday's attack comes five years after Las Vegas witnessed one of the worst mass shootings in recent US history.

Fifty-eight people died and hundreds were injured on October 1, 2017, when Stephen Paddock fired more than 1,000 rounds down on the crowd at an open-air country music concert while perched in a 32nd-floor room of the Mandalay Bay Resort and Casino in the city.

Paddock, a wealthy retired accountant, then shot himself in the head as police moved in.