TOKYO (AFP) - Japan's Prime Minister offered "heartfelt sympathy" on Thursday to those affected by the ferry disaster in South Korea, in a rare moment of detente between the feuding neighbours.

Divers were searching for nearly 300 people still missing 24 hours after the huge vessel capsized off the southwestern coast of South Korea, with hopes of finding any survivors fading. Six people have been confirmed dead.

Speaking at a forum in Tokyo, Mr Shinzo Abe, whose sometimes-abrasive nationalism has raised tensions between the two countries, said his thoughts were with those caught up in the tragedy.

"I extend my heartfelt sympathy towards people who were hit by the accident and their families," he said.

Relations between Seoul and Tokyo are at a low, beset by disputes over Japan's 1910-1945 occupation of the Korean peninsula - particularly the issue of the thousands of women forced into sexual slavery, the so-called "comfort women".

Mr Abe and South Korea's President Park Geun Hye have only met formally once despite both being in power for more than a year, and that only after United States President Barack Obama cajoled them into a three-way summit.

On Wednesday a senior Japanese diplomat visited Seoul for talks on the comfort women problem, with Japanese media reporting Tokyo was readying a package of measures it hoped would salve the row once and for all.

Referencing the delicate state of ties with Seoul, Mr Abe said on Thursday: "I (hope) to build a forward-looking relationship with President Park Geun Hye."