Human body parts fell from the sky in the Saudi city of Jeddah Sunday, with police saying they could be the remains of someone trapped in an aircraft's undercarriage bay.

"Police received a telephone call at 2:30 am from a witness reporting the fall of human remains at an intersection in Mushrefa neighbourhood" in the Red Sea city, spokesman Nawaf bin Naser al-Bouq said in a statement.

Initial indications were that the remains "fell from a plane's landing gear," said Bouq, adding that investigations were ongoing.

The report came after a Saudi Arabian Airlines jet made an emergency landing in the city of Medina in the west of the kingdom, injuring 29 people on Sunday.

That aircraft had been travelling from Iran's second city of Mashhad with 315 people on board.

A spokesman for the General Authority of Civil Aviation said there was no connection between the emergency landing in Medina and the Jeddah incident.

In a desperate attempt to cross borders, some people at poorly monitored airports climb inside the bays housing aircraft landing gear.

Most of them freeze to death once the aircraft reach cruising altitude, but some survive.

In 2010, the head of Beirut's airport security resigned after the death of a man who managed to hide in the undercarriage bay of a Saudi-bound jet.

The man's body was found by a maintenance worker who was inspecting the gear of the Saudi-owned Nas Air Airbus A-320 after it landed in Riyadh.