Yemen's Shi'ite rebels made advances Tuesday in southern Yemen, clashing with rival militias loyal to the country's current president.
The rebels -- known as Houthis -- entered the town of al-Dhalea and fought fierce gunbattles with militias who support Abd-Rabbu Mansour Hadi.
To the north in Taiz province, the rebels and soldiers loyal to ousted President Ali Abdullah Saleh clashed with anti-Houthi protesters. The soldiers opened fire on the protesters, killing at least one and wounding several others, according to medical officials.
These developments add to the conflict in Yemen, where rival factions in the north and south are pressing their fight for control.
The Houthis captured the capital, Sana'a, last September. Last month, Hadi escaped house arrest by the rebels in Sana'a and fled to Yemen's main southern city, Aden, to try to establish authority there.
Clashes have taken place in Aden between forces backing Hadi, and both those loyal to Saleh and the Houthi rebels.
The crisis in Yemen has drawn increased focus from other countries in the region and its allies overseas.
On Monday, U.S. Ambassador to Yemen Matthew Tueller said he is "relatively optimistic" a new power-sharing deal can be reached between the internationally recognized government of President Hadi and the Houthi rebels who control Sana'a. He told the Reuters news agency that decisions need to be made quickly.
"Political dialogue won't work if Hadi is overrun and captured, and Aden falls, which could happen very quickly," said Tueller.
Militia and security sources said Monday that pro-Hadi troops had fought off dozens of Houthis who had been sent toward Aden.
Saudi Arabia's Foreign Minister Saud al-Faisal said Arab countries would take "necessary measures" against the Houthis if a peaceful solution to the crisis cannot be found. He also condemned what he said was Iranian "interference" in Yemen.
The Shi'ite Houthis are accused of being backed by majority Shi'ite Iran, which is itself a regional rival of mainly Sunni Saudi Arabia.
Yemen has sunk into violence and chaos since a popular uprising ousted Saleh, the longtime strongman, in 2012.