Islamic State militants have stormed the office of international aid agency Save the Children in the eastern Afghan city of Jalalabad, killing at least two people and wounding 12 others.
In response to the January 24 attack, the London-headquartered organization had "temporarily suspended" all its programs across Afghanistan and closed its offices, a spokesperson said in a statement.
“It is with profound sadness that we can confirm three Save the Children staff members were killed earlier today in an attack on our office in Jalalabad, Afghanistan," the group said in a statement on January 24.
"All other staff have been safely rescued from the office. Four were injured in the attack and are receiving medical treatment," the statement said.
A suicide attacker detonated a car bomb outside the organization's provincial office in the eastern city after 9 a.m. on January 24, said Attaullah Khogyani, spokesman for the governor of Nangarhar Province.
A group of armed men then entered the building and battled security forces, Khogyani said.
Afghan special forces joined police to fight the attackers in a battle which continued into the evening, long after officials said it had ended.
The provincial governor's spokesman said five attackers were involved, all of whom were killed -- revising earlier accounts saying there were six attackers.
At least 46 people were rescued from the building by security forces, the spokesman also said.
The extremist group Islamic State claimed responsibility for the attack through its Amaq news agency, saying it targeted "British and Swedish foundations and Afghan government institutes."
A Swedish aid group office and a building of the Afghan Department of Women's Affairs are located near Save the Children's compound.
The assault comes after Taliban gunmen stormed a luxury hotel in Kabul on January 20, killing at least 30 people including 14 foreigners.
The Western-backed government in Kabul has been struggling to fend off militant groups since the withdrawal of most NATO troops in 2014.
The British ambassador to Afghanistan, Nick Kay, condemned the "horrific" attack, saying in a message on Twitter that "any attack on children & humanitarians is a crime against humanity."
The UN's Assistance Mission in Afghanistan tweeted that "attacks directed at civilians or aid organizations are clear violations of international humanitarian law and may amount to war crimes."
"An explosion rocked the area, and right after that children and people started running away," Ghulam Nabi, who was nearby when the bomb exploded, told Reuters. "I saw a vehicle catch fire and then a gunfight started."
Mohammad Amin, who was inside the compound when the attackers stormed in, told AFP that he heard "a big blast."
"We ran for cover and I saw a gunman hitting the main gate with a [rocket propelled grenade] to enter the compound. I jumped out of the window," he said.
Another witness said, "I am hearing gunfire from inside Save the Children compound."
Television news channels showed a plume of black smoke rising above the compound and what appears to be at least one vehicle burning outside the office.
An employee of Save the Children, who wanted to remain anonymous, was quoted as saying that around 100 people work at the building.
There are several other aid groups and government offices in the area, and security forces evacuated people from surrounding buildings while they battled the militants.
Jalalabad is the capital of Nangarhar Province, which borders Pakistan.
The province is a stronghold for the extremist group Islamic State and also has a significant Taliban presence.
Save the Children is one of the largest relief organizations in Afghanistan, where it carries out educational, health-care, and protection work for children.
Foreign aid groups working in Afghanistan have been targeted in the past.
The International Committee of the Red Cross announced in October that it would "drastically" reduce its presence in the country after seven employees were killed in attacks last year.