(CNN) -- Fierce battles between Yemeni government forces and Shiite Muslim rebels in the country's northwest have displaced tens of thousands of people, creating widespread humanitarian concerns, aid agencies said Thursday.
UNICEF trucks carrying supplies to internally displaced families in Yemen.
"The ongoing conflict in Saada has forced more than 100,000 people to flee their homes at great risks to their lives and well-being," said Ann Veneman of the United Nations Children's Fund. "Children and women represent the majority of the displaced."
The agency has been working to get refugees out of conflict zones and to provide them with safe drinking water, sanitation and critical supplies. The number of displaced could total as many as 150,000, Veneman said.
Getting assistance to those in need has been difficult, a government official said Wednesday.
"The government is cooperating with international relief organizations, with the U.N.," said Mohammed Albasha, a spokesman for the Yemeni embassy in Washington. "Internally we are doing all we can to ensure that civilians are not hurt and to minimize the collateral damage."
Yemen's government and Houthi rebels have been involved in intermittent fighting since 2004.
The conflict is believed to be both separatist -- over who will have power in the area -- and sectarian -- whether Shiite Islam will dominate even though the majority of Yemenis are Sunni Muslim. The Houthis are Shiites.
In mid-August, Yemen laid out cease-fire terms to the Houthi rebels, which included removing checkpoints, ending banditry and destructive acts, handing over all military equipment and weapons, and offering information on the fate of six kidnapped Europeans who disappeared in June, SABA, Yemen's official news agency reported.
Yemen's President Ali Abdullah Saleh is also faced with a separatist movement in the country's south and a growing threat from al Qaeda.
Al Qaeda in Yemen has been a growing concern for the United States.
In late July, Gen. David Petraeus, commander of the U.S. Central Command, and an accompanying delegation met with Saleh in Yemen. One of the topics of discussion was how to better combat terrorism, according to SABA.