International airlines have suspended flights to Yemen's capital, Sana'a, following days of heavy fighting between Houthi rebels and Sunni militias that has caused hundreds of residents to flee.
More than 40 people were killed in clashes overnight as rebel Houthi gunmen took over police and military patrol points in several parts of the city.
Yemen state owned media say the rebels shelled a state-owned television station Thursday in an attack that continued into Friday.
Reports say authorities have cut off mobile telephone and Internet connections in the capital, although landlines appear to be working.
The fighting is the most recent in a series of low-level clashes between Yemen's army and the Houthi rebels, which belong to the Zaidi Shi'ite sect.
The Houthis have led a campaign calling for the replacement of the government and economic reforms. Yemen's Sunni-majority government has accused them of being a proxy for Iran, blaming the mainly Shi'ite nation for sparking the unrest.