The plight of 28 Chinese fishermen who were kidnapped, robbed, stripped and held for 13 days by North Koreans has inflamed Chinese public opinion, with many Internet users taking to microblogging sites to question the Beijing government’s close relationship with its reclusive ally in Pyongyang.

But for the moment, experts and diplomats said, the episode seems unlikely to either shake the alliance or lead Beijing’s Communist authorities to heed Washington’s call to apply more pressure on North Korea to limit its nuclear ambitions.

The fishermen, who were in three boats, were seized May 8 in what the vessels’ owners said were Chinese waters. The Chinese Foreign Ministry did not report the incident for several days.

Since the fishermen’s release Sunday and their subsequent return to the Chinese port of Dalian, emerging details of their captivity have only intensified the public’s indignation. Wang Lijie, the captain of one of the seized boats, said in an interview Wednesday with The Washington Post that five fishermen remained hospitalized, their legs swollen from beatings received during their captivity. He described the captors as North Korean sailors, who gave the fishermen only grain to eat, stripped them to their underwear, beat them repeatedly and drained their boats of fuel before releasing them.

“This is the most horrible memory in my life,” Wang said. “They all wore deep-blue military uniforms, and they had a military flag on their boat. They were the North Korean navy.”

Wang said that he had encountered North Koreans in the past who were friendly but that this time, “they were even worse than bandits.” Noting that Pyongyang “is supposed to be a friend of China’s,” he added: “What happened to me this time changed my idea of North Korea completely.”

The fishermen’s accounts of mistreatment have also appeared widely in Chinese news media, which describe it as “torture.”

Shan Shixian, the owner of one of the boats, said in an interview that the kidnappers initially demanded a ransom of about $65,000 per boat but later just stripped the vessels and the men of everything they had. “They stole about one ton of fish on my boat, a dozen tons of diesel, my boat’s radar, the components, the battery and all the cargo,” Shan said. “Everything on the boat was looted.”

“I hate North Korea so much,” he said. “They not only robbed my fishermen, they tortured them. I’d kill them if I ever met any of them.” He added: “They are more like hooligans than the real hooligans. People are all scared.”

The sentiments of the captain and the boat owner were echoed even more vociferously on the Twitter-like microblogging site Weibo, which has emerged as China’s sounding board for public opinion. And public opinion has turned decidedly against North Korea, an ally considered so steadfast that Mao Zedong once said the relationship was “as close as lips and teeth.”

Some of the vitriol was aimed at the Chinese government.

“The anger burned in my heart when I saw this piece of news,” wrote one Internet user, posting under the name The Far Off Time. “North Korea always returns evil for good, and the Chinese government always swallows the humiliation and the anger.” The user added: “It’s all because the Chinese government is too weak. Who would dare do this to American fishermen?! Does the Foreign Affairs Ministry have any use?

Another user, writing under the name Unplugged Cat, wrote: “We raised a dog to watch the door, but were bitten by the crazy dog!”

A user named Zhuang Yuance asked, “Why should we shelter this bad neighbor against the will of people in most countries in the world? Will the North Korean people really appreciate us one day?”

The kidnapping was one of the hottest trending topics on China’s microblogging sites. That the Chinese government’s normally vigilant censors had allowed the open debate suggested that even Beijing’s leaders were becoming exasperated with Pyongyang.

China’s official media, meanwhile, have tried to play down the controversy, noting that all the crew members were eventually released and that no ransom was paid. An article in the Communist Party-owned Global Times newspaper Wednesday carried the headline: “Hype unnecessary over N. Korean sea action.”

Despite the online outcry, experts said they do not expect any immediate change in Beijing’s official policy of support for Pyongyang. China provides the destitute and isolated North Korea with most of its fuel, its food aid and its limited foreign investment. North Korea is also trying to crack open its doors to tourism as a source of cash, with the vast majority of tourists coming from China.

A U.S. delegation led by Glyn T. Davies, the special envoy for North Korea, visited Beijing this week but left for Tokyo without much apparent progress in persuading China to increase pressure on Pyongyang over its nuclear program. North Korea conducted its second nuclear test in May 2009, and U.S. officials have voiced concern that another test could follow soon.

But Shi Yuanhua, director of the Center for Korean Studies at Fudan University in Shanghai, said the fishermen’s case may have exacerbated the negative views of North Korea that the Chinese public began to express after the nuclear test, especially online.

“Chinese people may have a different attitude toward North Korea than the Chinese government,” he said.

“And as Chinese society becomes more and more open, it is not strange that Chinese people will form different opinions on North Korea. It’s a long-term process.”

Researcher Zhang Jie contributed to this report.