Banished Yemen President Abdrabbuh Mansour Hadi has backed to the southern city of Aden to supervise a new offensive against the rebel-held area of Taiz, officials say.
It is not clear how long Mr Hadi intends to remain in the country.
He made his first visit to Aden in September, having fled the country six months earlier in the face of advances by Houthi rebels.
At least 5,600 people have been killed in the past eight months of fighting.
A Saudi-led Arab coalition launched an air campaign in March, followed by a ground offensive, to push back the Houthis and reinstate Mr Hadi’s government.