The UN Security Council has called for an emergency meeting to discuss the situation in Yemen.
The UN spokesperson's office in an email said the council will hold a closed session on Sunday afternoon at 3 pm (1900 GMT) for consultations on Yemen.
On Saturday, Yemen's Shiite rebels issued a call to arms to battle forces loyal to the country's embattled president.
US troops were evacuating a southern air base crucial to America's drone strike program after al-Qaida militants seized a nearby city.
The turmoil comes as Yemen battles al-Qaida in the Arabian Peninsula, the target of the drone program, and faces a purported affiliate of the extremist Islamic State group that claimed responsibility for a series of suicide bombings killing at least 137 people Friday.