All 121 people on board a Cypriot airliner are feared dead after it plunged into a hill near Athens after an apparent drop in cabin pressure.

A text message sent from the plane said that the pilots were unconscious and passengers were freezing to death.

Greek F-16 fighter jets were scrambled when contact with the Helios Airways plane was lost during the flight between Larnaca in Cyprus and Athens.

Greek television said the plane's black box recorders had been recovered.

Relatives of some of the passengers gathered anxiously at Larnaca airport, and complained they had waited for hours without being told of their loved ones' fates.

"Tell us if our relatives are dead," some begged Helios officials. "Give us the names, we have waited too long."

But there was no confirmation of the identity or nationality of those on board.

"My son is a pilot and he flew to Athens today. I don't know what plane he was on," a distraught mother said.

However, a Greek police spokeswoman said there were no reports of survivors.

The Boeing 737 plane, carrying 115 passengers and six crew, came down at 1220 local time (0920 GMT).

Airline officials said the plane was due to fly on to the Czech capital Prague after a stopover in Athens.

A Greek police spokesman quoted by Reuters said of the passengers, 59 adults and eight children were heading to Athens, with 48 continuing on to Prague.

Larnaca airport authorities told Cyprus state TV a sudden drop in cabin pressure may have knocked out the pilots.

Greek TV reported that a passenger sent a text message to a cousin telling him that the pilot had turned blue in the face and the plane's temperature had plummeted.

"My cousin I bid you farewell, we are all frozen," the text message read.

There were initially suspicions the plane might have been hijacked, but these were swiftly ruled out by Greece's foreign ministry.

A Greek government spokesman said the first indication was that the crash was an accident.

The head of air traffic control at Athens airport, Iannis Pantazaratos, told AFP that authorities lost contact with the plane, and air force pilots found it flying above the Euboea peninsula with the pilots slumped in the cabin.

Rescue effort

Both Greek Prime Minister Costas Karamanlis and his Cypriot counterpart Tassos Papadopolous cut short holidays to return to Athens and Larnaca respectively.