One US serviceman has been rescued following a mid-air collision between two US military aircraft that took place at around 2am on  Thursday off southwestern Japan, according to Japanese Defense Minister Takeshi Iwaya.

However, six Marines remain missing, Reuters has reported.

The aircraft, an F/A-18 fighter jet and a KC-130 airborne tanker had taken off from Iwakuni Air Base, west of Hiroshima on the southern tip of Honshu, and are assumed to have been engaged in a refueling operation when they collided and crashed into the sea.

In a briefing to reporters, Iwaya said the rescued man, from the F/A-18, was believed to be in a stable condition. But search and rescue efforts were ongoing, he said, for six other US Marines still unaccounted for from the incident.

The Japanese Self Defense Force has deployed nine aircraft and three vessels for the search, Iwaya said. The Japanese Coast Guard is also engaged in the search and rescue efforts.

There are conflicting reports of the crash site. A US Marine press announcement said that it took place 322km (200 miles) off the coast, but Iwaya said it took place some 100km off Cape Muroto.

According to The Aviationist website, the F/A-18 is a twin-seat aircraft, while the KC-130 is a variant of the huge C-130, four-engine cargo plane. Both aircraft are operated by the US Marine Corps.

Some 50,000 US troops are stationed in Japan, with the most significant presence being the 3rd US Marine Expeditionary Force in Okinawa. Crashes, parts falling from aircraft and emergency landings on the island have contributed to tensions with locals, many of whom – including the island’s recently elected governor – are anti-US bases.

However, work is proceeding on a brand new base being built on reclaimed land off the Okinawan coast. By removing the current base from urban areas which have grown up around it, there are hopes that flight dangers will be ameliorated, but the new base has drawn opposition on environmental grounds.

with reporting by Agence France-Presse and agencies