"Indiscriminate attacks against civilians, including diplomatic envoys, are violations of human rights and international humanitarian law and cannot be justified," said a statement by UN Spokesperson Stephane Dujarric.
"The United Nations expresses its solidarity with the people and governments of Afghanistan and of the United Arab Emirates and calls for those responsible for the attack to be brought to justice," it added.
Two suicide blasts rocked Kabul earlier Tuesday, killing 28 people and injuring several others. The Taliban militant group has claimed responsibility for the attacks.
Also on Tuesday, two blasts hit the residence of the provincial governor of Kandahar. The ambassador of the United Arab Emirates to Afghanistan and the governor of Kandahar are reported to be among the injured.