Image copyright Reuters Image caption One of the two planes involved in the incident was a KC-130 refuelling tanker (like the one seen in this archive picture)

A big search and rescue operation is continuing in Japan for five missing US Marines after two aircraft with seven crew collided and crashed into the sea.

One Marine was rescued and was "in fair condition", while another one "has been declared deceased", Marines officials said in a statement.

The planes involved were a KC-130 and an F/A-18 based at Iwakuni near Hiroshima, south-western Japan.

US media say they crashed during a mid-air refuelling exercise.

The Marine Corps has not officially confirmed this, describing the incident as a "mishap".

How is the rescue going?

Japanese Defence Minister Takeshi Iwaya said Japanese aircraft and three vessels were taking partin the rescue operation.

The US 7th Fleet is supporting the operation, with navy aircraft being deployed.

Image copyright Reuters Image caption US aircraft and Japanese vessels are searching the area

A Marines statement said: "We are thankful for the Japan Maritime Self-Defence Force's efforts as they immediately responded in the search and rescue operation."

The Marines Corps tweeted that the incident occurred at about 02:00 local time on Thursday (17:00 GMT Wednesday).

The first Marine was rescued about four hours later, Japanese officials said, while the second was found 10 hours after the collision.

They said one of them was from the fighter jet.

There were five personnel on the C-130 and two on the F-18.

Japan said the search operation would continue overnight, Japan's NHK World reports.

It quoted the head of Japan's Self-Defence Forces,