There was no immediate confirmation of the crash from the defence ministry, which said it was gathering information on the report, or the US military.

The Kyodo news agency said the jet belonged to the US Kadena Air Base and crashed early Monday morning about 80 kilometres south of Naha, the regional capital of Japan's southern Okinawa island.

Japan's NHK television station said the rescued pilot had a broken leg.

Kadena is the largest US military base in Japan, which hosts around 47,000 American troops under a decades-long security alliance.

A series of accidents involving US military aircraft have stoked tensions and in January US Defence Secretary James Mattis apologised to his Japanese counterpart over the incidents.

They have included emergency landings by US military helicopters, a piece of a helicopter falling on a Japanese school ground, and a deadly crash last year of an MV-22 Osprey that forced a massive rescue operation.

Residents in Okinawa, which hosts the bulk of American troops in Japan, have protested against the deployment of Ospreys because of repeated accidents.

A series of crimes including rapes, assaults and hit-and-run and drink-driving accidents by US personnel have also triggered protests on Okinawa, and are a frequent irritant in relations between close security allies Japan and the United States.