"Our embassy in Sanaa remains at a high state of vigilance," he said in a statement Thursday. "We have been advising British nationals to leave Yemen since March 2011 and we continue to advise against all travel to the country."
Yemen's official Saba News Agency reported "a number of military personnel" were killed in a terrorist attack on the Defense Ministry in Sanaa. The Defense Ministry said "a number of armed men" entered the building after the explosion and exchange fire with Yemeni forces.
Hague said the attack shouldn't undermine progress made since 2012, when the government agreed to political reforms in the aftermath of democratic upheavals in the region the previous year.
Yemeni President Abdu Rabbo Mansour Hadi has pressed forward with a national reconciliation agenda since taking office in 2012.
"In a region which has seen huge instability and violence, Yemen's progress so far has been commendable and we must not allow this process to fail," Hague said.
Saba reported the situation was under control and most of the suspects were either killed or captured.