Militants stormed an office of the Save the Children aid agency in the Afghan city of Jalalabad and battled security forces who surrounded the building, leaving at least five people dead and 25 wounded.
The attack began with a suicide car bomb outside the office, followed by gunmen entering the compound and battling Afghan special forces, a spokesman for the government in the eastern province said.
IS has said it was behind the Save the Children attack in Afghanistan pic.twitter.com/SYro2hX3wA
— RTÉ News (@rtenews) January 24, 2018
Witnesses said there appeared to have been at least four attackers in police uniform, a commonly used tactic, but there was no official confirmation.
The director of the provincial health department said 12 wounded people had been taken to hospital.
As security forces fought their way in, they recovered one body inside the compound but its identity was not clear. A member of the security forces was also killed.
A witness, who was nearby when the bomb exploded, said: "An explosion rocked the area and right after that children and people started running away.
"I saw a vehicle catch fire and then a gunfight started."
There was no immediate claim of responsibility but the Taliban, seeking to reimpose Islamic rule after their 2001 ousting, issued a statement denying involvement.
There are several other aid groups and government offices in the immediate area. Security forces evacuated people from surrounding buildings while they exchanged fire with the militants.
A Save the Children spokesman said they are devastated at news of the attack.
"Our primary concern is for the safety and security of our staff. We are awaiting further information from our team and cannot comment further at this time."
Jalalabad is the capital of Nangarhar province, on the porous border with Pakistan.
The province has become a stronghold for the Islamic State group, which has grown to become one of Afghanistan's most dangerous militant groups since it appeared around the beginning of 2015.
Backed by intensive US air strikes, Afghan forces have claimed growing success against the Taliban and other militant groups, including Islamic State, but militant attacks on civilian targets have continued, causing heavy casualties.
The attack in Jalalabad came just days after Taliban militants attacked the Hotel Intercontinental in the capital, Kabul, killing at least 20 people, including 13 foreigners.
The attack underlines how difficult operating in Afghanistan has become for humanitarian aid organisations, which have faced heavy pressure from armed groups and kidnappers.
In October, the Red Cross announced that it was drastically reducing its operations in Afghanistan following attacks that killed seven of its staff last year.
