An attacker who defaced the Web site of Turkey's embassy in China on Monday left behind a pro-China note as the two countries worked through a diplomatic spat.
The Web site is also loading slowly, possibly signalling a denial-of-service attack, where a site is bombarded with traffic. The attacks are apparently retaliation for Turkish criticism of China over deadly riots last week, when members of the Uighur ethnic minority clashed with Han Chinese, China's majority ethnic group.
The riots in western Xinjiang province left at least 184 people dead and over 1,600 injured, according to the state-run Xinhua news agency.
Turkish Prime Minister Recep Tayyip Erdogan last week called the events "a kind of genocide," and the country's trade minister called for a boycott of Chinese goods.
Thousands of Turks reportedly demonstrated in support of Chinese Uighurs over the weekend.
Uighurs' links to Turkey include a Turkic language and their dominant religion, Islam.
The message left on the defaced Turkish embassy Web site demanded that Turkey not meddle in Xinjiang affairs, which it called China's "internal matter," according to a screenshot on the Web site of China's state-run Global Times newspaper.
The message, written in red text on a black background, also said the Chinese people would not be afraid if Turkey wanted to harm them with a boycott in order to gain entry to the European Union.
The message had been removed by Tuesday, but users of Chinese chat forums said in posts that they had also seen the defaced Web site. Some left supportive messages.
"Whichever hacker you are, I admire you!" one user wrote in a forum run by local portal NetEase.com.
A person at the Turkish embassy said the Web site had loaded slowly for two days but could not confirm whether it was attacked or defaced. The site is low security and only meant to give information to local Chinese, the person said.
Chinese Internet users have launched nationalistic attacks on foreign Web sites in the past, including against CNN last year. Those attacks, sparked by what many Chinese saw as biased Western media coverage of an uprising by monks in Tibet, were strong enough to slow access to the news site in the U.S.
Demands for greater autonomy in Xinjiang and Tibet are hyper-sensitive issues in China, which sees separatism and foreign intervention in domestic politics as among the greatest threats to its rule.
China cut off Internet and mobile phone service in Xinjiang after the riots last week to prevent further unrest. It also blocked social Web sites including Twitter and Facebook across the country.
Turkish cyberattackers have targeted Chinese Web sites before, though hacking between the countries has not been a hot-button issue.
The five hacker groups or individuals that defaced the most Chinese Web sites last year were all Turkish, according to a report from China's National Computer Network Emergency Response Technical Team.
The Turkish attackers often use images that are pro-Islam and blast Israeli and U.S. policies to deface Web sites, both in China and elsewhere.
But the attackers may not always have political motives.
Turkish hacker groups, among the most active worldwide in defacing Web sites, often do it simply for fun, said Konstantin Sapronov, head of the Kaspersky Virus Lab in China.