DANDONG, China - Trucks rumbled across the Chinese-North Korean border Thursday in a sign that trade was continuing despite Beijing's anger over the North's avowed hydrogen bomb test, which could spark economic retaliation and further estrangement between the once-close communist allies.

There were no obvious signs of disruption in the northeastern city of Dandong that sits on the Yalu River directly across from North Korea's Sinuiju. The twin cities are the conduit through which much of North Korea's international trade passes.

China condemned Wednesday's purported test, which sent tremors across parts of northeastern China near the North Korean border and alarmed residents.

"I think it is a threat and sabotage to China and to the world peace for such a country to own nuclear weapons," Dandong resident Tian Zhibin said in an interview with The Associated Press on Thursday.

Analysts say Beijing will likely join other members of the UN Security Council in imposing tougher economic sanctions on its communist ally.

Beijing could also introduce unilateral measures such as tighter inspections of the trucks that cross the Yalu carrying mostly consumer goods bound for the North. China-North Korean economic projects could be suspended and Chinese companies and banks discouraged from doing business with North Korea.

Yet as North Korea's neighbour and chief backer, Beijing is unlikely to takes steps that might seriously undermine Kim Jong Un's hard-line communist regime. Apart from a traditional friendship dating back decades, China is fearful of a collapse that could bring chaos, sending refugees across the border and possibly leading to a U.S. military presence in the North.

Although willing to notch up sanctions, Beijing likely won't reduce energy and food assistance or impose overly harsh economic sanctions, said Bonnie Glaser, an expert on China at the Center for Strategic and International Studies think-tank .

"Economic relations and nuclear issues are likely to remain on two separate tracks," Glaser said.

Despite the ups and downs in relations, China continues to have a vested interest in maintaining friendly ties with Pyongyang. Apart from providing material assistance, that includes defending North Korea from condemnation at the United Nations over its human rights abuses and designating refugees from the North as economic migrants rather than asylum seekers.

For Beijing, the North Korea issue is not simply one of nuclear proliferation, but also of peninsular stability, the balance of power in Northeast Asia and its growing rivalry with the United States, said Jingdong Yuan, an Asia-Pacific security expert at Australia's University of Sydney.

"Rather to live with a bad situation than to leave it completely to chance and lose all control," Yuan said.

But even with that sense of resignation, China still needs to consider increasingly negative public opinion toward Pyongyang, analysts say.

The state-run China Daily said in an English-language commentary that, if proven, Pyongyang's actions were "irresponsible and reckless."

The nationalist tabloid Global Times emphasized the danger to social stability in northeastern China, which lies as close as 50 kilometres (30 miles) from the test site. Schools and office buildings were evacuated after residents were shaken by the magnitude 4.8 earthquake caused by the detonation. Technicians were also monitoring the air for signs of contamination.

"Pyongyang must consider the long-term negative impact on Beijing-Pyongyang ties and its own development," the Global Times said.

While China's total control over the media and public discourse allows it to squash such opinions at any time, in this case "a bit of strategic stirring by the Chinese Communist Party of limited public resentment at North Korea seems to make sense," said Adam Cathcart, a specialist in China-North Korea relations at Britain's University of Leeds.

That's especially true when the issue involves environmental damage or the threat of radiation along the border, Cathcart said.

"Call it the Fukushima effect," he said, a reference to fear and outrage in China over Japan's 2011 nuclear crisis.


Associated Press writer Christopher Bodeen in Beijing and video journalist Wong Wai-bor in Dandong, China, contributed to this report.