CHINESE state media and netizens alike have joined the government in condemning Japanese Prime Minister Shinzo Abe's visit to the Yasukuni war shrine, with analysts predicting a more robust response to come from China.
Emotions also ran high in South Korea, whose ties with Japan have already been testy over various issues, and security around the Japanese embassy in Seoul was beefed up in anticipation of incidents today.
China's official Xinhua news agency, in one of two commentaries released hours after Mr Abe's visit yesterday, called it "a grave provocation that may lead to heightened tension in the region".
"Choosing a sensitive time to visit a highly controversial and notorious place, Abe knows perfectly what he is doing and the consequences," wrote Xinhua.
China's Internet users were peeved that Mr Abe chose to visit the shrine on the day Chinese leaders like President Xi Jinping were attending public events marking the 120th birth anniversary of late strongman Mao Zedong.
One user said the shrine visit signals Mr Abe's aim to remilitarise Japan and invade countries like in World War II, saying: "If we are not aware of this possibility, our future generations could one day become war slaves."
Observers say China is set to unleash greater anger, compared with its restrained reaction the last time a serving Japanese premier visited the shrine. Mr Junichiro Koizumi did so in 2006 shortly before stepping down, but Beijing reportedly reined in public sentiment then to focus on a post-Koizumi era.
But there are new factors now, such as the Japanese government's nationalisation in September last year of some of the Diaoyu/Senkaku islands, to which both sides have claims.
Also, China could be more motivated to castigate Mr Abe's visit, which it views as more damaging than Mr Koizumi's in 2006 - though the latter had done so on Aug 15, a sensitive date marking Japan's surrender in World War II.
Mr Koizumi's annual visits during his 2001-2006 term to Yasukuni, which honours war criminals among 2.5 million war dead, had angered China and South Korea. Both view it as a symbol of Japan's past militarism, under which both countries suffered.
But Mr Abe's actions and rhetoric - defending Japan's wartime aggression, signalling intentions to revise its pacifist Constitution and expanding Japan's defence budget for the first time in 11 years - show him to be more dangerous, said Peking University analyst Wang Dong.
"Abe's main reasons for visiting the shrine are a reflection of what he truly believes: The history of Japanese imperialism is glorious and it is his 'historical mission' to restore that 'pride' in the hearts of Japanese people," Professor Wang told The Straits Times.
Rising nationalistic sentiment could trigger stronger retaliatory measures from China, said China Foreign Affairs University analyst Zhou Yongsheng. There could be a return of a boycott of Japanese products and Beijing could deploy more ships and planes to patrol the disputed islands, he said.
One thing is for sure: The remote chance of a meeting between Mr Xi and Mr Abe, a call made repeatedly by the latter, has dipped further, said analysts.
In Seoul, the Koreans have only angry words, with Culture Minister Yoo Jin Ryong saying: "Our government cannot repress condemnation and rage over Prime Minister Abe's paying of respects at the Yasukuni shrine that glorifies its colonial aggressions and enshrines war criminals."
Netizen "wnet" added: "We should halt all trade and relations with this criminal country."
Additional reporting by Andrew Salmon in Seoul