A passenger on a small plane from Belize on Thursday shot dead an American armed with a knife who was attempting a hijacking, police in the Caribbean nation said.

The would-be hijacker threatened the pilot shortly after the Cessna Grand Caravan from Belize's Tropic Air took off in the morning with 14 on board from the town of Corozal.

It was headed for the Belizean island of San Pedro, but the man ordered the pilot to head "out of the country," police commissioner Chester Williams told Channel 5 news.

The plane hovered for some time over the international airport of Belize City before landing just as it was about to run out of fuel, at which point the hijacker stabbed two fellow passengers.

One had a firearm he was licensed to carry, and shot the attacker dead, according to officials and local media.

Police identified the assailant as 49-year-old US national Akinyela Sawa Taylor, who was apparently a military veteran.

The injured passengers were taken to the hospital.

The US Embassy in Belize expressed its regret over the incident on the eve of the Easter long weekend.

"It really highlights the importance of safety and security," the embassy's public affairs officer Luke Martin told reporters.

"We have a strong relationship with Belizean law enforcement, and in times like this, that partnership proves crucial," with a quick exchange of information, he added.