An American F-15 fighter jet has crashed into the sea off the island of Okinawa in southern Japan.

The F-15C Eagle based out of Kadena Air Base in Okinawa crashed in the sea off the Japanese island at around 6.36am local time on Monday, and the pilot was safely recovered after ejecting, the Air Force confirmed in a statement.

The pilot remained in contact with rescuers after ejecting and is now recovering in stable condition at a military hospital in Okinawa, a US Air Force official said.

A US Air Force F-15 is seen in 2009 taking off at Kadena US Air Force Base on Japan's southwestern island of Okinawa. A similar plane crashed there on Monday

The F-15 developed technical problems in flight, and the cause of the crash is under investigation, Lt Col David Honchul, the chief spokesman for the US forces in Japan, told the Independent.

A Japanese Self Defense Force helicopter participated in the rescue effort in cooperation with the US military.

Japanese Coast Guard vessels are also said to be responding on the scene.

'Huge thank you to the Japan Air Self-Defense Force search and rescue team out of Naha Air Base this morning,' Kadena Air Base said on Twitter.

'Your quick response proves once again how valuable an asset you are to the U.S./Japanese alliance.'

There are roughly 50,000 US military personnel based in Japan, about half of them in Okinawa.

The incident comes as President Donald Trump travels in East Asia for a summit with North Korean leader Kim Jong Un in Singapore.

It is the 12th US military aircraft crash so far this year. The last F-15 based out of Kadena to crash was in 2006.