TOKYO (REUTERS) - Japanese Emperor Akihito and his wife bowed their heads and offered prayers on Tuesday (March 27) for victims of World War Two in Okinawa, on what could be their last visit to pay respects on an island where 30 per cent of the population died in the war.

The emperor, who has spent much of his nearly three decades on the throne seeking to soothe the wounds of war, will step down on April 30 next year in the first abdication by a Japanese emperor in nearly two centuries.

The three-day visit to the southwestern chain of islands is the 11th by the imperial couple and their first since 2014, when they came ahead of the 70th anniversary of the Battle of Okinawa.

More than two months of fighting between US and Japanese troops in 1945 killed about a third of the island's people.

"He really thinks deeply about Okinawa, that's why he can come so often," Naeko Teruya, 84, a survivor of the battle, told NHK public television.

Five members of Teruya's family were killed in the fighting, including her father.

Akihito and Empress Michiko laid flowers at a memorial in Itoman city, where one of the fiercest final battles took place, bowing deeply.

On Wednesday, they will visit the island of Yonaguni, the westernmost point of Japan.

Okinawa residents lived under US rule for 27 years after the war. Today, it hosts nearly 75 per cent of the US military presence in Japan, a devil's bargain that has brought jobs but has also worry about crime and military accidents.

The imperial couple first visited Okinawa in 1975, when painful memories of the war - fought in the name of Akihito's father - were sharper and attitudes towards the imperial family complicated.

He became the first Japanese monarch to visit in 1993 after assuming the throne in 1989.

Akihito, 84, said in 2016 he feared age might make it hard for him to fulfil his duties. He will be succeeded by his heir, 58-year-old Crown Prince Naruhito.