Japan's defense ministry has said two Russian fighter jets briefly breached its airspace off the northern tip of the island of Hokkaido, forcing Japanese fighters to scramble in response. Russia denied the intrusion.
The two Russian planes were detected for just over a minute Thursday. Defense ministry official Yoshihide Yoshida said it was not immediately known whether the violation was intentional or accidental, but that it was "extremely problematic."
Japan's foreign ministry filed a formal protest over the intrusion by two Russian Su-27 fighters, the type pictured above.
"Today, at around 3:00 pm (0600 GMT), military fighters belonging to the Russian Federation breached our nation's airspace above territorial waters off Hokkaido's Rishiri island," the foreign ministry said.
Yoshida said it was the first such violation in five years, with the last one taking place on February 9, 2008.
Russia denied its fighter jets had entered Japanese airspace, saying it was holding military exercises in the area.
"Flights of military aircraft are … carried out in strict accordance with the international rules of governing airspace and do not violate the border of other states," a Defense Ministry spokesman, Colonel Alexander Gordeyev, told the Interfax news agency.
Thursday was Japan's "Northern Territories Day," when rallies are traditionally held calling for the return of the disputed islands off Hokkaido, known as the Southern Kurils by Russia.
Japanese Prime Minister Shinzo Abe had told a rally of around 2,000 former islanders and their descendents that he would move forward with negotiations with Russia for the return of the islands.
"I had telephone talks with President [Vladimir] Putin in December, and told him I would like to work to find a mutually acceptable solution to this last-remaining major problem between Japan and Russia," Abe said.
"The government intends to follow its basic policy of settling the territorial issue and then sign a peace treaty," he added. "We will press ahead with negotiations with strong will so that progress will be made towards the conclusive end of the territorial problem."
Soviet forces seized the islands in the final days of World War II, driving out Japanese residents. They were later repopulated by Russians, but remain a poor and undeveloped part of the country.
dr/hc (APF, Reuters, AP)