Afghanistan's ruling Taliban militia has expelled 20,000 people from villages north of Kabul since Friday, burning homes and crops and forcing the refugees to trek 25 miles to the capital, U.N. officials said today.

Secretary General Kofi Annan condemned the scorched-earth campaign, part of a military offensive aimed at crushing the last pockets of resistance to the Taliban's rule and extending its extreme Islamic regime over the entire country. The Taliban controls about 85 percent of Afghanistan.

U.N. officials said they have received first-hand accounts from new arrivals in Kabul that the Taliban's forces burned entire villages in the Shomali plain and Panjshir valley. Another major influx of homeless villagers is expected in the capital in the next few days, the officials said.

The United Nations also reported that at least 1,000 of the new arrivals, primarily ethnic Tajik men, have been arrested in Kabul.

"The secretary general is deeply distressed by reports of widespread violations of human rights," said Manoel de Almeida e Silva, Annan's spokesman. "He also expresses deep concern over reports of the involvement in the conflict of students, some as young as 14."

The Taliban offensive, which began in late July, is aimed at the forces of Ahmed Shah Masood, an ethnic Tajik commander who enjoyed U.S. support during the anti-Soviet war in the 1980s. The fighting started just a week after the United States, Russia and Afghanistan's neighbors persuaded the factions to meet in peace talks in Tashkent, Uzbekistan.

"Masood is the last major focus of conventional resistance to the Taliban," said a U.S. State Department official. "He is the toughest nut, and they are trying to break his power. But what we are seeing are indications that even if they manage to defeat him, they will still face ongoing resistance all around the country."

Abdul Hakeem Mujahid, the Taliban's representative in the United States, denied that the Taliban has forcibly expelled civilians from their homes. He said that enemy fighters, recruited from local villages, have sent their relatives to Kabul for protection.

"They come to Kabul because they consider themselves and their families secure and safe," said Mujahid. "Houses that are strongholds of the opposition may have come under fire, but civilians and the common people? That is absolutely wrong."

The offensive threatens to increase the political isolation of the Taliban, which has never been recognized by the United States or the U.N. as Afghanistan's legal government. The United States and Russia, rivals on many issues at the U.N., have begun to consider U.N. sanctions on the Taliban.