Taiwanese President-elect Tsai Ing-wen’s Facebook page was bombarded with tens of thousands of pro-China comments late Wednesday, in what appears to be an unprecedented effort by mainland Internet users to bypass Chinese Internet controls and launch a coordinated messaging campaign on the hot-button issue of cross-strait ties.

Members of Baidu Tieba, a message board run by Chinese Internet giant Baidu, collectively scaled China’s Great Firewall beginning at 7 p.m. Wednesday and flooded Ms. Tsai’s official Facebook page with anti-Taiwan independence messages.

The campaign -- which also targeted the pages of more than 10 organizations including Taiwan and Hong Kong media outlets Sanlih E-Television and Apple Daily as well as the British Broadcasting Corporation – appears to represent a new strategy by mainland Internet users to organize their message and swarm online media blocked in China.

“This is a self-organized cultural communication from members of Liyi Ba,” the organizers of the campaign wrote in a statement on their official Weibo microblog, using the name of the Baidu Tieba message board they belong to. “We aimed to close the cognitive gap between netizens from both sides.”

The effort comes less than a week after Ms. Tsai swept to victory in Taiwan’s presidential election on Saturday, in a win that brings to power her Democratic People’s Party (DPP), which espouses Taiwan’s formal independence from China. Beijing claims the self-governed island as its territory.

Liyi Ba, also known as Di Ba, is an online community with more than 20 million members, according to Baidu – a figure that rivals Taiwan’s 23 million population.

By midnight Wednesday, five hours after the online posters began their coordinated effort, the latest posting on Ms. Tsai’s official Facebook page had received more than 35,000 comments, most of which were messages indicating that Taiwan is a part of China.

The number of participants is unknown. But according to statistics shown on Tencent QQ, a popular online instant messaging service which also served as an organizing base for the participants, at least 4,000 Internet users were involved. More than 60% them are members of China’s post-1990 generation, according to a China Real Time analysis of the statistics.

The effort was particularly noteworthy for its level of organization. Internet users leading the campaign divided participants into work groups and assigned them different tasks, such as collecting photos, making graphics (or "stickers") and clicking “like” on others’ postings.

A screenshot of pro-China comments on Tsai Ing-wen's Facebook page on Jan. 21, 2016.

Organizers also urged participants to be “civilized” and “reasonable” in their postings. Some users appeared to oblige, posting photos of China’s gorgeous tourism spots and delicious food along with captions such as “Made in China.”

Others, however, crossed over into more combative territory. They posted messages such as "Fight with Taiwan Independence dogs,” "Your mainland father will fix you,” and "What a stupid (expletive) you are.”

One 21-year old organizer who declined to give her name said that participants were instructed to refrain from “liking” more-radical comments and those using offensive language. “We hope to leave them with a peaceful, friendly and generous ‘great-nation’ image,” she told China Real Time.

Meanwhile, other Internet users have debated whether the participants are just members of a young “cyber mob” driven by nationalism. One hour after the attack, the hashtag “Di Ba goes to battle on Facebook” was the top-ranked hashtag on Weibo, with nearly 800,000 followers.

Chinese Foreign Ministry Spokesman Hong Lei referred questions about the campaign to the government’s Taiwan Affairs Office. A spokesman for the office declined to comment.

Jing Yue, a philosophy Ph.D. student at the University of St. Andrews who often discusses China’s political ecology, declared in a message on his Weibo account that the incident shows that “the mission of the Great Firewall is gone,” as the censorship apparatus was originally intended to prevent Chinese people from viewing “anti-China” messages such as those related to Taiwan independence.

He added that those taking part in the campaign had climbed the firewall “just to mock free people with their stickers and slogans from Cultural Revolution era.”

Shi Anbin, a communications professor from Tsinghua University, said the campaign is reflective of “an ideological war between the two sides.”

"Nationalism is a dominating ideological trend driving the Chinese millennial generation,” while young people in Taiwan are more post-materialistic, he said.

Wang Zhikai, 22, one of the organizers who wrote the official statement, hinted that the message board users are preparing for an even larger-scale mission in the future. “We are now optimizing our team in order to achieve a bigger goal,” he said.

Taiwan’s new ruling party, meanwhile, appeared to take the incident in stride. Asked for comment, the DPP’s Department of International Affairs quoted the party’s spokesman, Yang Jialiang, as saying: “Welcome to the free and democratic Taiwan; that is all.”

--Marco Huang