At least two people have been killed in an explosion near Sanaa University in Yemen, Al Jazeera has learned.
An improvised explosive device went off on Tuesday in Yemen's largest city, also injuring at least two people, the sources said.
A security official said the blast happened during an event commemorating the country's 1990 unification, adding that the death toll was expected to rise.
The event was reportedly organised by the Houthis, who have controlled Sanaa since September 2014 despite a 14-month-old Arab military intervention in support of President Abd-Rabbu Mansour Hadi.
The unification of the country on May 22, 1990, came after centuries of separation between the north and the south, where British colonial rule was followed by a Soviet-backed communist government.
There was no immediate claim for Tuesday's bombing but both al-Qaeda and the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group have carried out past bombings against the Houthis, whose faith they regard as heretical.
Suicide bombings claimed by ISIL in March last year killed 120 worshippers at mosques frequented by the Houthis.
Tuesday's blast followed a day of heavy bloodshed in the Arabian Peninsula country: a double bomb attack on would-be army recruits killed at least 45 people in the southern city of Aden.
Monday's attacks were claimed by the local affiliate of ISIL.
Source: Al Jazeera