Japanese Prime Minister Fumio Kishida is expected to visit South Korea in the coming weeks and meet with President Yoon Suk-yeol, officials have said, reciprocating a Tokyo visit by the South Korean leader last month.

A Japanese government official and another official from a Group of Seven government said the meeting was expected before Kishida hosts a G7 summit from May 19.

Japan's Kyodo news agency said on Saturday the two will meet around May 7 or 8, citing multiple unnamed Japanese and South Korean diplomatic sources.

Their aim will be to confirm the two neighbours' strengthening of cooperation over North Korea ahead of the Hiroshima G7 summit, Kyodo said.

Asked about reports of the bilateral summit, Kishida said in remarks broadcast by public network NHK that nothing concrete had been decided.

An answering machine at Japan's foreign ministry on Saturday said no one was available over the weekend.

Improving ties

Ties between Japan and South Korea, long strained by issues including wartime compensation and trade, have been improving in recent months due to North Korea's frequent missile launches and China's more muscular role on the global stage.

The two sides agreed to revive shuttle diplomacy when Yoon met with Kishida in Tokyo in March, the first Japan visit by a South Korean president in 12 years.

The last visit by a Japanese prime minister to South Korea was made by Shinzo Abe in 2018, according to NHK.

US President Joe Biden this week praised Yoon's efforts toward improving relations with Japan during a visit by Yoon to Washington. Biden, Yoon and Kishida are to meet on the sidelines of the Hiroshima summit, according to Japanese media reports.

North Korea's Kim Yo-jong, the powerful sister of leader Kim Jong-un, said a US-South Korea agreement this week about the need to shore up South Korean security will worsen the situation, according to state media KCNA.

North Korea is convinced it must further perfect a "nuclear war deterrent" as a result, Kim was quoted as saying.