KABUL, Afghanistan — The Taliban insurgency has spread through more of Afghanistan than at any point since 2001, according to data compiled by the United Nations as well as interviews with numerous local officials in areas under threat.

In addition, the United Nations Assistance Mission in Afghanistan over the past two weeks has evacuated four of its 13 provincial offices around the country — the most it has ever done for security reasons — according to local officials in the affected areas.

The data, compiled in early September — even before the latest surge in violence in northern Afghanistan — showed that United Nations security officials had already rated the threat level in about half of the country’s administrative districts as either “high” or “extreme,” more than at any time since the American invasion ousted the Taliban in 2001.

That assessment, which has not been publicly released but is routinely shared by the United Nations with countries in the international coalition, appears at odds with the assessment of its American commander, Gen. John F. Campbell, in his testimony to Congress last week.