NEW YORK (AP) _ The area's three major airports were under tightened security today because of a threat of terrorist attack by Middle Eastern militants, possibly a ``suicide massacre.''

Travelers headed to Kennedy, LaGuardia and Newark airports were told to allow more time for security checks and not to leave cars unattended at terminals. Also, vehicles were subject to random searches.

The heightened security was imposed after the FBI learned that terrorists had targeted Kennedy, a major international arrival and departure point, according to a report first published Sunday in Newsday.

Unidentified officials told Newsday the FBI had received detailed intelligence that two militant groups _ the Palestinian Hamas and the Iran-backed Hezbollah, or Party of God _ were planning a ``suicide massacre'' that could come at any time.

The threat comes at a time when the United States has begun proceedings to extradite a reputed Hamas leader, Mousa Abu Marzuk, to Israel. Also, a group of Islamic fundamentalists are on trial in New York on charges of conspiring to plot terrorist acts.

A State Department official who requested anonymity told The New York Times that ``whatever threats we have received'' have come from within the United States.

The FBI relayed its information to the Port Authority of New York and New Jersey, which operates the three airports, on Saturday afternoon and security at Kennedy was immediately brought up to its highest level, Newsday said.

Security at Kennedy was raised to ``Level 4'', an action not taken since the Gulf War in 1991, Newsday and the Times said. The New York Post said all three airports were at Level 4.

On Wednesday, federal Transportation Secretary Federico Pena announced new airport precautions nationwide to ``deter possible criminal or terrorist acts.''

As part of that national alert, the airport at Ithaca, N.Y., 175 miles northwest of New York City, was closed for a time this morning after a man described as a Turkish national was seen looking into parked cars, said Stephan Nicholson, the airport assistant manager. The man was charged with loitering.

At Kennedy's International Arrivals Building, only people with tickets were allowed to enter the departure wing and long lines formed as employees checked passengers.

However, Kennedy's operations desk said no flight delays were reported as of early today.

Trash cans that might hide explosives were removed. A rooftop parking lot at the Delta Airlines terminal was closed.

At all three airports, tow trucks were sent out to remove unoccupied cars, and vehicles were subject to random searches.

Car and truck bombs, sometimes set off by suicidal drivers, are a favored method of some Middle East terrorist groups.

FBI spokesman Joe Valiquette would not comment this morning on any aspect of the security measures or confirm the Newsday report. Tom Middlemiss of the Port Authority referred all inquiries to the Federal Aviation Administration. The FAA did not immediately return calls.

D. Joy Faber, a spokeswoman for the Port Authority, said there was no telling how long the measures would remain in effect.