AFGHAN TROOP TOLL AS HIGH AS 140

Militants, some posing as wounded soldiers, attack a base in the city of Mazar-i-Sharif. The Taliban claims responsibility.

KABUL, Afghanistan — More than 100 Afghan soldiers, many having just finished prayers, were killed when militants disguised in army uniforms infiltrated a base in northern Afghanistan and opened fire, Afghan defense officials said Saturday.

The attack, for which the Taliban claimed responsibility, was one of the deadliest to strike Afghan forces in years and illustrated the continuing lethality of an insurgency now in its 16th year.

The Taliban said that 10 assailants carried out the Friday afternoon attack, which aimed to avenge the deaths of two of its top officials in northern Afghanistan at the hands of Afghan forces.

An Afghan provincial military official said the death toll could be as high as 140.

Some of the attackers posed as wounded soldiers and joined an army convoy as it drove to the northern city of Mazar-i-Sharif, said the official, who requested anonymity because he wasn’t authorized to speak to the media.

Other attackers also posed as soldiers and already had infiltrated the Afghan army’s 209th Corps in Mazar-i-Sharif, the capital of Balkh province and long known as one of the safest major cities in Afghanistan.

The assailants approached a mosque in the compound as soldiers were leaving the Friday prayer, as well as a nearby dining hall, the official said. The facilities both were filled with hundreds of soldiers, most unarmed.

The militants sprayed the base with gunfire before being shot and killed by Afghan commandos from the elite Crisis Response Unit.

Afghan President Ashraf Ghani visited the base Saturday and condemned the attack, calling the assailants “infidels.”

The Afghan Defense Ministry said its forces were engaged in heavy fighting against militants in northern Afghanistan and had reeled off a string of recent victories.

Afghan soldiers and police “will extend these operations until the terrorists are finished,” the ministry said in a statement.

The U.S.-led military coalition said Saturday that it had carried out an airstrike Wednesday in the northern province of Kunduz that killed a senior Taliban official and eight other Taliban fighters. The U.S. military has increased its campaign of airstrikes in northern and eastern Afghanistan in recent months targeting the Taliban and followers of Islamic State, the militant organization based in Iraq and Syria.

The attack on Afghan soldiers followed a raid last month on the country’s main military hospital in Kabul, the capital, that left 50 people dead. Islamic State’s regional affiliate claimed responsibility for that attack, but officials still are investigating the claim.