Provincial governor’s spokesman Attaullah Khogyani said that clashes at the education department have ended. He said so far 11 people were killed and 10 others wounded in the hours-long attack, reports confirmed.
Gunmen attacked an education department office in the eastern Afghan city of Jalalabad on Wednesday and were holding out against security forces who had surrounded the compound, officials said.
Two explosions were heard near the scene and at least two people had been killed and five wounded, the provincial governor's office said.
However, with an unknown number of people trapped in the building, the final casualty figure may be much higher.
"Our first priority is to rescue those people who are stuck inside," Jalalabad police chief Ghulam Sanayi Stanekzai told Tolo News TV.
It was the third major attack in less than two weeks in Jalalabad, the main city of Nangarhar province, following a blast that killed a group of Sikhs on July 1 and a second that killed at least 12 people on Tuesday.
The attacks have underscored the instability in many parts of Afghanistan following a brief three-day truce with the Taliban over the Eid al-Fitr holiday last month.
Backed by intensive US air strikes, Afghan forces have claimed success in holding the Taliban back from major cities and US commanders say they have been hitting other militant groups like Islamic State hard.
But attacks on civilian targets have continued, causing heavy casualties.
There was no immediate claim of responsibility for Wednesday's attack but both of the other assaults in the city this month were claimed by Islamic State, which is opposed to both the Western-backed government in Kabul and the Taliban.
The attack on the education department appeared to be following the pattern of previous attacks including an assault on an office of the Save the Children aid group in Jalalabad in January and another on the city accounts office in May.
Nangarhar province, on the porous border with Pakistan, has become a stronghold of Islamic State, which has grown into one of Afghanistan's most dangerous militant groups since it appeared around the beginning of 2015.