The official reason was that Macedonia could no longer cope with the influx. But there was also speculation that the move was a reaction to the government's failure to win more aid from the International Monetary Fund.
Aid workers were dismayed. "The border was closed. We were given no notice. We think people were either not allowed in or pushed back into no-man's land," said Paula Ghedini of the United Nations High Commission for Refugees.
Another UN official suggested that the move was aimed at forcing the pace at which refugees already in Macedonia were deported or airlifted. "They will reopen the border at some point but I think they [the refugees] will get a one-way ticket to Albania," he said.
There was also concern that Macedonia, which has been critical of the international community's handling of the crisis, would try to move refugees off its territory by force during the night.
Earlier Dennis McNamara, UNHCR special envoy for the region, appealed to Albania to accept 60,000 more Kosovars from Macedonia. He said refugees may soon arrive at camps without shelter in what he described as a "least worst scenario".
During the past five days, Serbian forces have been sending three trains a day to the Blace border, taking refugees at the rate of 10,000 every 24 hours. The latest arrivals are from Glogovac, Obilisk and Podujevo, areas that until now had not been ethnically cleansed.
"People talk of being forced from their homes and put on coaches to Pristina, where they were packed into trains," Ms Ghedini said. "We are picking up stories of atrocities and mass graves from people."
The new arrivals have walked into a desperate situation. Camps are overflowing. The newest, Cegrane, which has been open for five days, has 28,500 residents, who have to share latrines at a ratio of 245 to one. The recognised limit is 15 to one.
Across the border in Albania, despite UN efforts to move refugees south, the camps in Kukes are filled with Kosovars who refuse to leave the area, despite the threats posed by Albanian bandits and Serbian artillery.
Meanwhile, in what seemed to be a warning that refugees could be stuck in Albania and Macedonia for the winter, Nato's Supreme Commander, General Wesley Clark, said that Nato and the aid agencies must make "full provision for the realities of the terrible tragedy perpetrated against Kosovo Albanians... even when they're allowed to go home, life won't be normal for a while, so I think that we have to look very much ahead, past the summer, into the autumn, the winter and even the next spring."Reuse content