A man was arrested for trying to hijack a plane flying from Botswana to South Africa on Monday, South African police said.

Police spokesman Senior Superintendent Vish Naidoo said a 26-year-old man armed with two "items" demanded to be let into the cockpit but posed no real threat to passengers.

South African radio SAFM said the man banged on the door of the cockpit and threatened to blow up the plane, which was carrying 23 passengers and 4 crew members, but police said the man had no bomb and was not armed with serious weapons.

"A man was alleged to have attempted to hijack a Botswana airliner, but while the passengers and crew may be highly traumatised, there was no real danger to them," Naidoo said.

"He demanded the cockpit door be opened. He was armed with two items but they posed no real threat."

Naidoo said police were alerted and the Air Botswana flight from Gaborone landed as scheduled at Johannesburg Airport at about 6:10 p.m. (1810 GMT), where he was arrested.

The man, whose identity and nationality were withheld, was being questioned by police.

Naidoo said police did not know the motive for the attack but said there was no evidence to suggest the man was linked to al Qaeda or part of any "international plot".

Passengers on board the flight were being questioned by police and Naidoo said he was unable to provide further details.