Image copyright Vulcan Inc Image caption Sonar imaging reveals intricate details about the Akagi, which is lying about 18,000 feet (5,490 metres) under water

Deep sea explorers have found two Japanese aircraft carriers that were sunk in battle in World War Two.

The carriers were among seven ships that went down in the Battle of Midway, a major air and sea battle fought between the US and Japan in 1942.

One ship, the Kaga, was discovered last week, while wreckage from another carrier, Akagi, was found on Sunday.

Until now only one other ship sunk in this battle had ever been found - the American vessel USS Yorktown, in 1998.

This month's discoveries came after weeks of searching by crew members based on the research vessel Petrel. The vessel is owned by Vulcan Inc, a company created by the late Microsoft co-founder Paul Allen.

The crew deployed an autonomous underwater vehicle (AUV) fitted with sonar, which helped to pinpoint the locations of the Kaga and Akagi.

Image copyright U.S. Naval History and Heritage Command Image caption The Akagi aircraft carrier was sunk during the Battle of Midway, during which hundreds of Japanese and US sailors died

The Petrel also worked with the US Navy, as according to US law it is otherwise illegal to disturb underwater war graves - that is, sites where the wrecks of US military ships lie.

Both ships were found lying about 18,000 feet (5,490 metres) under water within the Papahanaumokuakea Marine National Monument - the largest marine conservation area in the world.

Image copyright Vulcan Inc Image caption Pictures reveal large sections of the boats are still intact, like this gun mount from the Kaga

Midway Atoll, a small group of islands in the North Pacific, was used as a US military installation during the war.

Japan had planned to capture the islands after its surprise attack on a US base in Pearl Harbour. But America intercepted its communications, and when Japanese troops arrived at the islands on 4 June 1942, they found the Americans waiting to meet them.

More than 2,000 Japanese people and 300 Americans were killed in the battle that ensued, and a total of seven ships were sunk - four of which were Japanese carriers.

America's victory at Midway dealt a huge blow to Japan's naval capabilities and was seen as a turning point in the Pacific War.