NEW YORK - A tour helicopter carrying five Italian tourists collided with a small plane Saturday over the Hudson River near Manhattan, and authorities believed all nine people aboard were killed.

The accident, which Mayor Michael Bloomberg called "not survivable," scattered debris into the river and onto the Hoboken, New Jersey, waterfront. It happened just after noon (1600 GMT) between Manhattan and Hoboken on a clear summer day.

Two bodies were recovered in the water, one floating free and one in the wreckage. Other bodies have been spotted in the debris. The crash victims included five Italian tourists and a pilot on the helicopter and the three people on the plane, including a child, Bloomberg said.

"This is not going to have a happy ending," Bloomberg said. He said he thought it fair to say "this has changed from a rescue to a recovery mission."

The plane, a Piper PA-32, took off from Teterboro Airport in New Jersey, and the helicopter was a Eurocopter AS 350 owned by Liberty Tours, a sightseeing and charter company, the Federal Aviation Administration said.

The plane was headed to Ocean City, New Jersey, FAA spokesman Jim Peters said. The helicopter had just taken off from a heliport on Manhattan's West side.

People who saw the crash and its aftermath described the two aircraft colliding not far from the Hoboken shoreline, and said the impact sheared off the plane's wing.

"There was a loud pop, almost like a car backfire," said Buzz Nahas, who saw the crash from Hoboken. "The helicopter dropped like a rock."

Katie Tanski, of Hoboken, heard the noise of the collision, looked up and saw chaos in the air.

"We saw the helicopter propellers fly all over," she said. Some pieces of the wreckage fell on land, sending Tanski and others scurrying for cover.

On the New York City side of the river, Melissa Green, 33, and her husband were having lunch in a park along the Hudson when they heard the collision.

"We heard first a huge crash, a boom almost. We turned around and saw these two mushroom splashes," Green said. "What was really weird is there was no wreckage, nothing."

"I hope they find the people, but I don't know. They just disappeared," Green said.

Seven months ago, the same river was the scene of a spectacular aircraft accident that resulted in no loss of life. In January, a US Airways flight taking off from LaGuardia Airport slammed into a flock of birds and lost power in both engines.

The plane crash-landed in the Hudson River, and all 155 people on board were pulled to safety.

A person who answered the phone at a Liberty Tours office declined to comment on the accident, but said the company would be releasing a statement. The company runs sightseeing excursions around the Statue of Liberty, Ellis Island and Manhattan at costs ranging from $130 to about $1,000.

Two years ago, a Liberty helicopter fell 500 feet (150 metres) from the sky during a sightseeing trip. The pilot was credited with safely landing the chopper in the Hudson and helping evacuate her seven passengers.

In 1997, a rotor on one of its sightseeing helicopters clipped a Manhattan building, forcing an emergency landing. No one was hurt.

A small plane has collided with a tour helicopter over the Hudson River and New York Mayor Michael Bloomberg says it's believed that all nine people are dead.

Bloomberg says the crash victims include five Italian tourists and a pilot on the helicopter and three people on the plane, including a child.

Bloomberg says officials believe the accident was "not survivable."

Two bodies have been recovered in the water, one floating free and one in the wreckage. Other bodies have been spotted in the debris.

The mayor says "it's fair to say that this has changed from a rescue to a recovery mission."

The accident happened in a busy general aviation corridor in which pilots operate freely at a low altitude and keep an eye out for other aircraft by sight.

Two people at New York City emergency response agencies say at least one person is confirmed dead and they know of no one being rescued from the aftermath of a plane-helicopter collision over the Hudson River.

The officials spoke on condition of anonymity because they are not authorized to speak before Mayor Michael Bloomberg gives a media briefing.

About nine people were believed to be on board the two aircraft.

The Coast Guard had earlier reported one rescue.

The accident happened just after noon between Manhattan and Hoboken.