NEW YORK CITY (AFP) - The United States Federal Bureau of Investigation (FBI) says its antiterrorism unit is investigating lasers that have increasingly been targeting commercial airplanes arriving at New York City's airports.

The incidents - which "can temporarily or permanently blind a pilot and crew" - have increased 17 per cent since last year, according to the statement from the federal law enforcement agency dated on Friday.

The two latest incidents happened on Tuesday. The first, at 7.35 pm local time, involved a flight with regional carrier Shuttle America.

"The aircraft cockpit was illuminated by a green laser" as it approached La Guardia airport, while it was around 10km away, the FBI said.

The laser beam came from the Bronx, according to the crew.

In the second incident, three hours later, a private aircraft reported another green laser coming from Queens, around 3km south-west of La Guardia airport.

No one was injured in Tuesday's incidents, but "several commercial pilots earlier this year suffered significant injury, including a burnt retina", the FBI said.

The agency "is asking anyone with information about any of these dangerous laser incidents to pick up the phone and call us", Mr George Venizelos, a top FBI official in New York, said.

"Our paramount concern is the safety of aircraft passengers and crew."

The statement said the agency is offering a reward of an unspecified amount for information leading to an arrest and conviction.

According to the Federal Aviation Authority, laser incidents have been increasing for several years. Across the US, some 3,592 incidents were reported in 2011, up from 2,836 incidents the year before.

It is a crime in the United States to point a laser at an airplane - punishable with jail time and a fine up to US$11,000 (S$13,600).

The FBI's Joint Terrorism Task Force, which is leading the investigation, comprises more than 50 local, state and federal agencies.