The death of Kim Jong-il has altered the peculiar form of commerce that takes place along the Tumen river, a ribbon of ice separating North Korea from China.

Across a short bridge from Namyang, in the northernmost tip of North Korea, laden coal trucks crossed into China as usual.

However, the assembled Chinese tour groups, who are normally allowed to walk to the halfway point, had to stop at the bridge’s entrance. The border guard, with no visible weapon, said, smiling sheepishly, that this was out of respect to North Koreans grieving the death of their “Dear Leader”, Kim Jong-il.

At the bridge’s entry point, they could linger for photographs or choose from plentiful North Korean trinkets – Kim pins were selling well – and gaze at the drab buildings and scrubby hills on the other bank.

If China had fears about an imminent collapse of the North Korean regime, it was doing a good job of hiding them. “What’s dangerous about this? Our relationship with the North Koreans has always been friendly,” said Hu Xin, a man visiting from Shanghai with a bulky zoom lens on his camera.

That has been the message from the Chinese leadership since Kim’s death was announced. The government has also pledged its support for Kim’s successor, Kim Jong-eun, and made clear that it wants stability in North Korea above all else.

Beijing has long worried that the North Korean regime disintegrating could unleash a wave of refugees. The fact that the Chinese government now appears relatively relaxed stems from its judgment that the father-to-son transition need not be immediately destabilising – and its confidence that it has already gone a long way to locking down the 1,416-km border.

Frozen solid and just 50 metres wide, the upper reaches of the Tumen in December once made a perfect crossing for refugees from desolate and starving North Korea. Analysts say the numbers probably peaked in the late 1990s. But double layers of barbed-wire fences on the Chinese side and patrol towers dotting the North Korean side – many of which locals say were recently built or reinforced – have made the illegal crossings more difficult.

“I used to pick them up fairly regularly on the streets. You could spot them by their clothes,” said Wang Yanqing, a taxi driver. “They wouldn’t speak any Chinese but would give me papers with place names, and then someone would greet them and pay the fare. But there haven’t been any over the last two or three years.”

Without a doubt, Kim’s death has provoked some heightened military alert. On the highway just south of the city of Tumen, near a narrow stretch of the river, two armoured vehicles and 15 soldiers had set up a checkpoint. However, their sole activity was blocking foreign reporters from proceeding.

At the same time as staunching the flow of refugees, China has tried to expand commercial ties with North Korea. Their bilateral trade rose 30 per cent last year to a record high of $3.5bn, according to Chinese data. Compared with China’s trade with other countries, though, those numbers are tiny and progress is patchy.