Clashes between Houthi rebels and pro-government forces killed or injured dozens of people across south Yemen Saturday, including civilians, while a cease-fire is set to expire late Sunday.
Violence in the city of Taiz claimed at least 12 lives and injured dozens more in what Yemeni government officials said was rebel shelling of several neighborhoods.
The Houthis signed on to the tenuous five-day truce initiated by Saudi Arabia, which has been leading an air campaign against the militant group since late March in support of the exiled President Abd Rabbu Mansour Hadi.
Riyadh has repeatedly accused the Houthis of violating the cease-fire in the last week.
What began as an internal conflict in Yemen has spiraled into a regional one, with accusations that Iran is backing the rebels that took over parts of the country and ousted the president earlier this year, as Saudi Arabia leads a cross-border military intervention.
Iran's Supreme Leader, Ayatollah Ali Khamenei, said Saturday he will continue to help "oppressed" people in the region, including Yemen.
The extent of Tehran's involvement with the Houthis remains unclear.
Ongoing violence and a Saudi-led blockade have hindered access to ports, runways and roads, severely limiting humanitarian aid to millions of Yemenis.
More than 1,500 people have been killed since Saudi Arabia began its bombing campaign in March.