Japan has summoned its ambassador to China back to Tokyo as tensions in the East China Sea escalate, the Financial Times reports.

Ambassador Uichiro Niwa previously expressed his concern, during a Financial Times interview in June, over Tokyo’s plan to purchase the Senkaku Islands, saying that it could instigate an “extremely grave crisis” between Japan and China. The comment angered conservatives – including some Diet members from opposition groups and the ruling Democratic party – and called for Mr. Niwa to be replaced. Government leaders dismissed the comment as “personal opinion”, saying it does not reflect the government position.

Foreign Minister Koichiro Gemba’s decision to call back Mr. Niwa reflects Japan’s hardline stance on asserting its sovereignty over the islands, according to the Wall Street Journal. “We want to talk directly with Mr. Niwa regarding the current situation in Japan-China relations and his analysis of it,” Mr. Gemba said in an All-Nippon News Network broadcast.

Kyodo news agency quoted Mr. Gemba as saying Mr. Niwa’s return was only temporary and should not be seen as a protest against China. “I again instructed him to accurately convey Japan’s thinking,” Mr. Gemba told reporters after meeting with Mr. Niwa on Sunday.