KABUL, Afghanistan — Taliban insurgents dealt a serious blow to one of the Afghan Army’s most highly regarded units on Friday, killing 13 soldiers and overrunning their remote outpost in eastern Afghanistan.

According to Afghan security officials, speaking on the condition of anonymity because of the nature of the Taliban victory, the 13 soldiers constituted the entire complement at the checkpost. One police official said that a force of 200 Taliban fighters had opened fire with heavy weapons and finally set the post on fire; most of the deaths were from the flames.

It was one of the bloody insurgent attacks in the current spring offensive that have helped drive the rate of government fatalities to the highest level of the war. Afghan soldiers and police officers are dying at more than double the rate of a year ago, according to military officials.

The numbers both underscore how much more of the fighting has been handed over to Afghan forces and raise questions about how ready those forces are for the increased responsibility, even as the insurgents ratchet up their much-anticipated spring onslaught.