A suicide bombing has taken place inside the UN's World Food Program offices in Islamabad, the Pakistani capital, killing at least three people.
One Iraqi and two Pakistani women working for the World Food Program (WFP) died and several others were injured in the explosion on Monday.
No claim of responsibility for the attack was immediately made.
"I was on the upper floor when there was the sound of a huge explosion downstairs. I found many of my colleagues lying on the floor full of blood," a WFP employee who declined to be named, said.
The UN said that it had closed its offices in Pakistan since the attack, although no specific threat had been received.
Kamal Hyder, Al Jazeera's correspondent in Islamabad, said: "This building is heavily fortified. On the outside it is completely bunkered with bomb proof walls around it.
"According to the reports we are getting there were over 50 people inside the building.
"A bomb or explosive device is said to have gone off inside the building. We can see that the front door has been taken out, the windows are shattered. But there appears to be no structural damage.
"Some smoke is still billowing out [of the building]. The explosive itself does not seem to have been a powerful one.
"We were told that many of the wounded were immediately rushed off in private vehicles, some belonging to the WFP itself. Then ambulances arrived."
PHOTO CAPTION
Security forces stand guard outside the U.N. World Food Program (WFP) offices in Islamabad, after a suicide bomber struck inside the compound October 5, 2009.
Al-Jazeera