The border is closed to people, but not goods, and a 600-bed isolation hospital is being built.

On Wednesday, China reported 59 imported cases of Covid-19 across the whole country. According to state media, 25 of them entered the country via Suifenhe - making the remote north-east crossing something of a hotspot.

The patients were all returning Chinese citizens who had flown from Moscow to Vladivostok, a Russian city around 100 miles south. All the new patients were taken to hospital, with two in a serious condition. In addition, another 86 people in Suifenhe - who came via the same route - were classed as "asymptomatic" but positive for the virus, which China counts separately.

The border was closed to people on Tuesday, the local government said, although cargo can continue. Russia closed its border with China In February.