A threatening letter against Israeli airline El Al has been found at Zaventem Airport over the weekend, news agency Belga reported on Monday.

According to the federal police, the letter was found in a toilet block at the airport.

A police spokesman said security patrols were reinforced in response.

"The patrols are armed as per normal," he said, but refused to reveal how many extra officers are on patrol.

The exact nature of the threat is not known.

Belga reported that the public prosecution office has launched an investigation and was expected to release further details about the matter later.

It said the letter is probably a reaction to the Israeli military offensive in Lebanon.

Meanwhile, El Al said it has not strengthened its security, stressing that safety precautions have been extremely tight for many years.

The check-in counter at El Al is open as normal and no flights have been cancelled or delayed, Belga reported.

(Xinhua News Agency August 1, 2006)