The blast was one of a series of attacks in three cities in Afghanistan which killed at least 50 people and wounded dozens.
Five officials from the United Arab Emirates (UAE) have been killed in a bomb attack in southern Afghanistan.
The UAE ambassador to Afghanistan was also injured in the blast in the city of Kandahar, which killed at least 11 people.
It happened at the guesthouse of a provincial governor inside a heavily guarded compound.
The officials had been involved in "a mission to carry out humanitarian, educational and development projects", according to the UAE's official news agency WAM.
The Taliban has denied planting the bomb, blaming the attack on "internal local rivalry".
The federation of seven emirates, including Abu Dhabi and Dubai, said flags would be flown at half mast for three days of mourning.
Dubai's ruler Sheikh Mohammed bin Rashid Al Maktoum, the UAE prime minister and vice president, wrote on Twitter that "there is no human, moral or religious justification for the bombing and killing of people trying to help" others.
Abu Dhabi's powerful crown prince, Sheikh Mohammed bin Zayed Al Nahyan, said the attack wouldn't stop UAE's humanitarian efforts.
The Kandahar blast was one of a series of attacks in three Afghan cities which killed at least 50 people and wounded dozens of others.
In Kabul, a suicide bomber blew himself up and a car bomb was detonated near the Afghan parliament, and in Helmand province a suicide bomber targeted a guesthouse used by an intelligence official.
At least seven people were killed there.
Taliban insurgents have escalated their campaign of violence in Afghanistan in recent days, as winter takes hold.
UAE troops were involved in the NATO-led mission in Afghanistan, and the Gulf federation also trained members of the Afghan armed forces.
NATO officially ended its Afghanistan operation in December 2014, but US forces still based there were granted greater powers in June to strike at armed groups.