SEOUL, Oct. 17 (Xinhuanet) -- South Korea's Foreign Minister Ban Ki-moon summoned Japanese Ambassador to Seoul Shotaro Oshima on Monday to file a protest over Japanese Prime Minister Junichiro Koizumi's visit to a war shrine earlier in the day.

In the meeting, Ban expressed his "deep regret and disappointment" over Koizumi's visit to the shrine, which honors war criminals of the World War II, reported South Korean Yonhap News Agency.

"It is not too much to say that the biggest obstacle to the estranged relations between South Korea and Japan is Prime Minister Koizumi's visits to the Yasukuni Shrine," Ban said.

Ban also asked the Japanese ambassador to convey to Koizumi andJapanese Foreign Minister Nobutaka Machimura Seoul's deep regret and disappointment over the shrine visit, according to Yonhap.

Ban underscored that Koizumi's repeat visits to the shrine destroyed the two nations' efforts to further thaw their relations.

He urged again Koizumi and other Japanese officials not to visit the shrine, saying "It glorifies war criminals who brought indescribable agony and damage to neighboring Asian nations."

Listening to Ban's remarks through an interpreter, the grim-faced Japanese ambassador said nothing during the first part of the meeting that was open to the media, said Yonhap.

After about 10 minutes of open talks, the two officials held brief discussions behind closed doors.

Earlier Monday, Koizumi made a visit to the Yasukuni Shrine, where 2 million Japanese war dead, including 14 Class-A war criminals from World War II, are honored. The visit was the fifth since he took office in 2001.

South Korea's Foreign Ministry also issued a statement denouncing the shrine visit.

Relations between South Korea and Japan turned strained in the first half of this year due to their dispute over a group of islets located in the East Sea (Sea of Japan).

The islets, called Dokdo in Korean and Takeshima in Japanese, have been the fuse of disputes between the two nations.

As an effort to improve relations, South Korean President Roh Moo-hyun and Koizumi held summit in June here this year, in which the Japanese premier agreed to consider building an alternative memorial for the Yasukuni Shrine.

Koizumi made similar remarks during a summit with former South Korean President Kim Dae-jung in 2001, but with no follow-up actions.