Tokyo on Tuesday condemned a surprise visit to Moscow by a Japanese lawmaker who met with Russia's deputy foreign minister.
Muneo Suzuki's trip, the first known visit by a Japanese lawmaker since Russia invaded Ukraine last year, comes after Japan joined Western allies in sanctioning Moscow over the conflict.
"The government wasn't briefed by Suzuki on the Russia visit this time, before or after," spokesman Hirokazu Matsuno said.
"We're issuing a warning... of canceling travels to Russia and no matter what the purpose is, we're urging all citizens to refrain from traveling to Russia," Matsuno told reporters.
Russia's Foreign Ministry said Suzuki met with Deputy Foreign Minister Andrei Rudenko on Monday.
"The Russian side noted a significant contribution by the Japanese MP to the development of the bilateral ties," the ministry statement said Tuesday.
"We regretfully state that the legacy of two countries' cooperation, accumulated over decades, is being purposefully destroyed by the sanctions policy implemented by Tokyo in order to please the United States and the anti-Russian course of the 'collective West'," it said.
Suzuki, a member of the center-right opposition Japan Innovation Party, is a longtime advocate of close Japan-Russia ties.
He was deeply involved in the foreign ministry's programs aimed at solving territorial disputes with Russia after World War II.
The upper house member departed for Moscow on Sunday "for an inspection tour," his secretary Shinji Akamatsu told AFP.
Suzuki "is visiting from the viewpoint of national interest based on his own belief," Akamatsu said.
Suzuki's party will meet with the lawmaker once he returns, a party official said, hinting that the lawmaker may have breached a party rule by failing to submit travel plans before his departure.
The ruling Liberal Democratic Party's secretary general Toshimitsu Motegi said Suzuki's visit is "not desirable."
Suzuki was forced to leave the LDP in the early 2000s after being hit by bribery and political funding scandals.