SANA'A, Yemen - Shiite rebel forces captured new territory in Yemen on Sunday after a call to arms from their leaders, pressing south toward the headquarters of the country's embattled president and pitching the country further toward sectarian war.

Local officials said Houthi forces had seized the airport in the central city of Taiz, sparking concerns that they were planning a push toward Aden, the port city 120 miles further southwest, where President Abed Rabbo Mansour Hadi has set up a rival governing authority after being driven out of the capital.

After a week of escalating conflict, the U.N. Security Council held an emergency meeting on Sunday to address the crisis, which has resulted in the United States withdrawing its remaining military personnel from the impoverished country.

The U.N. special envoy for Yemen, Jamal Benomar, warned at the meeting that events appear to be leading the country "to the edge of civil war" and urged all parties to step back from the brink and resolve the conflict peacefully, the Associated Press reported.

Benomar stressed in a video briefing from Qatar that neither the Houthis nor their opponent, Yemen's president, could realistically expect to establish control over the whole country.

With rival regional powers of Shiite Iran and Sunni Saudi Arabia backing opposing sides, the struggle has taken on an increasingly sectarian tone.