Heavy artillery clashes between Yemen's dominant Houthi rebel group and local fighters shook the southern cities of Taiz and Dalea on Monday, residents said, and a Yemeni official said UN peace talks set for Geneva later this week had been delayed.
Militiamen seized the main security directorate and strategic mountaintop buildings from the Houthis in Dalea, a bastion of a secessionist movement in Yemen's formerly independent south, much of which has been destroyed in more than two months of fighting.
Ten soldiers loyal to the Houthis and three southern militiamen were killed, fighters and residents said.
In the southern city of Taiz, Houthi fighters pushed back tribal and Islamist militiamen amid heavy street combat, and Arab air raids hit a military base loyal to Houthis in the capital Sanaa on Monday.
A Saudi-led coalition has been bombing the Iran-allied Houthis for months and supporting Yemeni fighters opposing the groups in battle lines drawn across the country. Saudi Arabia and Gulf powers are concerned that the Houthi Shi'ite Muslim movement's allegiance to Iran will give the Islamic Republic a foothold in the Arabian Peninsula.
Yemen's exiled government in Saudi Arabia led by President Abd-Rabbu Mansour Hadi has demanded the Houthis recognise its authority and withdraw from Yemen's main cities — two points demanded by a U.N. Security Council resolution last month.
Those demands may have pushed back a UN-sponsored negotiations set for Geneva on May 28.
"The Geneva meeting has been indefinitely postponed because the Houthis did not indicate their commitment to implement the UN Security Council resolution," Sultan al-Atwani, an aide to President Hadi, told Reuters by telephone from Riyadh.
"Also, what is happening on ground — the attacks on Aden, Taiz, Dalea and Shabwa makes it difficult to go to Geneva," he added, naming southern provinces that have become war zones.
Ahmad Fawzi, spokesman for the UN in Geneva, said he could not confirm the reports of a delay to talks, saying that plans were still underway for negotiations to start on Thursday.
