An Afghan woman walks past a vehicle at the International Committee of the Red Cross office in Kabul in 2008. (Shah Marai/AFP/Getty Images)

Six staffers of the International Committee of the Red Cross were killed and two others are missing after their convoy was ambushed by unidentified gunmen in northern Afghanistan, the humanitarian agency said Wednesday.

No group immediately claimed responsibility for the attack, the deadliest against the ICRC in Afghanistan, but local officials blamed the Islamic State, which is known to have militants operating in the area. The Taliban, which also is fighting the U.S.-backed government in Kabul, denied any involvement in the ambush.

The attack underscored the deterioration of security in Afghanistan, where insurgents have been battling Afghan government and foreign forces since the Taliban was driven from power in late 2001.

[U.N. says civilian toll in Afghanistan is highest in years]

The Islamic State claimed responsibility Wednesday for a separate attack — a suicide bombing Tuesday evening that killed at least 22 people outside Afghanistan’s Supreme Court in Kabul, news agencies reported.

The ICRC said the attack on its personnel occurred near Shebergan, capital of the northern province of Jowzjan. The province bordering Turkmenistan has been known as one of a handful of relatively secure areas in northern Afghanistan.

The team of five field officers and three drivers was in a convoy to deliver livestock materials in an area south of Shebergan, the ICRC said in a statement. An Afghan employee of the ICRC said the team was trying to help people affected by this week’s heavy snowfall in the region.

[Heavy snow causes scores of deaths in Afghanistan]

“This is a despicable act. Nothing can justify the murder of our colleagues and dear friends,” said Monica Zanarelli, head of the ICRC delegation in Afghanistan.

The ICRC later said it was temporarily suspending operations in Afghanistan, putting its fourth-largest humanitarian program on hold. Thomas Glass, an ICRC spokesman in Kabul, described the attack as the deadliest for the organization in Afghanistan since it began working in the country 30 years ago.

In December, a Spanish employee of the ICRC was kidnapped in the restive province of Kunduz. He was freed safely after a month of captivity.

Taliban insurgents denied responsibility for that abduction as well.

Taliban spokesman Zabiullah Mujahid promised that the group would assist in “finding the perpetrators,” Reuters news agency reported.

The Jowzjan provincial police chief, Rahmatullah Turkistani, said the ambush was probably the work of Islamic State militants, the Associated Press reported. The provincial governor, Lotfullah Azizi, told Reuters that the Islamic State “is very active in that area.”

[The Islamic State is gaining ground in Afghanistan]

If the group’s responsibility is confirmed, the ambush would mark the first known Islamic State attack on an international organization in Afghanistan since its emergence in the country in late 2014.

The Islamic State’s activities have been mostly confined to eastern areas of Afghanistan, although it has claimed deadly attacks this year against Shiites, mostly in Kabul.

Affiliates of the group are largely made up of Pakistani militants driven into Afghanistan after a military crackdown in their country, according to Afghan officials.

The Islamic State “tends to resort to exceptional attacks at the start of its emergence for the sake of propaganda,” said Bashir Bezhan, an Afghan analyst. “It wants to show its presence through such an attack, cause concern among people, particularly among aid groups, and frighten them to pack and go.”

William Branigin in Washington contributed to this report.

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