Wreckage from the civilian plane

JERUSALEM (CNN) -- Fearing a terrorist attack, Israel said it shot down a small plane and killed its pilot Thursday after it crossed into its airspace from Lebanon.

Israeli said the pilot ignored repeated warnings to turn back before being shot down. Lebanese authorities said the student pilot, Estephan Nicolian, took the aircraft up without his instructor.

Nicolian's motives for flying the Cessna 152 towards Israel are not known, but Israeli officials said they shot the plane down because they feared a terrorist attack.

"We have to remember that as long as our territory is violated, we have the right to respond from time to time," Maj. Gen. Dan Halutz, an Israeli air force spokesman, said Thursday.

The plane was shot down south of Haifa on the anniversary of Israel's withdrawal from southern Lebanon, a tense day that found Israeli forces on high alert and involved in deadly clashes with Palestinians in Gaza.

Israeli and Lebanese authorities gave differing accounts of the incident, which began when light plane took off from Beirut International Airport with just the student pilot on board.

Lebanese officials described Nicolian's flight as a joyride.

Officials said the trainee arranged a lesson, went to the aircraft and started down the runway when the instructor's back was turned. At least one employee of the flying school unsuccessfully chased the plane on the runway, they said.

Lebanon said Nicolian was intercepted by Israeli aircraft over its southern border town of Tyre and was forced to fly south into Israel. Israel said the plane was already over Israeli airspace when Israeli helicopters intercepted it, and its aircraft never crossed the international border into Lebanese territory.

The wreckage landed in the seaside community of Mikhmoret, Israel, south of Haifa.

IDF officials said the pilot did not respond to more than 15 minutes of repeated warnings issued by Israeli helicopters and F-16 fighter jets for the Lebanese plane to turn around. Military officials also said eye contact was made with the pilot.

Nicolian was killed when the plane was shot down

Also Thursday, Israeli forces clashed with Palestinians in Rafah, Gaza, with the Palestine Red Crescent and Israeli Defense Forces giving differing accounts of the incident.

The Red Crescent said Israeli forces razed a home and opened fire on stone-throwing residents in a refugee camp in Rafah. Two Palestinians, one 15 and another 18, were shot and killed, and others were injured.

Israeli military officials said the army never bombarded the refugee camp and never went into Palestinian territory. The military said only that Israeli forces are near Rafah, in an area under full Israeli control, and were returning heavy fire from the Palestinians.

Earlier, Israeli officials said two mortar shells were fired on the Jewish settlement of Netzarim in Gaza.