A man has been held at Karachi airport after batteries and an electrical circuit were found in his shoes as he tried to board a plane, reports say.

Mohammad Munir, spokesman for the airport security force, said the civil engineer was arrested when a scanner sounded an alarm at the airport.

He was scheduled to travel to the Omani capital Muscat on Thai Airways.

The suspect was not found in possession of explosives, but Mr Munir described the circuit discovery as "worrying".

He told AFP news agency: "After the machine gave the alarm, we checked him manually.

"We have recovered four live batteries and a circuit, with a button to switch it on and off."

The arrested man is said to be a Pakistani citizen in his 30s.