Story highlights The U.N. Security Council backs Yemen's embattled President

U.N. envoy says Yemen is in a "rapid downward spiral," urges dialogue

Houthi rebels have taken over the Taiz airport and set up checkpoints nearby

Sanaa, Yemen (CNN) Rebels seized an international airport in Yemen Sunday as a U.N. envoy warned that the country was at "the edge of civil war."

Houthi militants took over the airport in Taiz as they swept through the city and surrounding province, two officials with the Taiz provincial government said.

One civilian was killed and 82 others wounded when the rebels fired at local residents protesting their presence, the officials said.

The rebels have also seized security and intelligence buildings in Taiz and set up checkpoints in the area, the officials said. Taiz, about 390 kilometers (240 miles) south of Sanaa, is Yemen's cultural capital.

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