Houthi fighters ride in a truck. Reuters

Houthi fighters are poised to enter Yemen's second city of Aden as reports abound that Yemeni president Abdrabbuh Mansour Hadi has fled to Saudi Arabia.

AP and AFP reported Wednesday that Hadi had left Aden as the Shia Houthi army advanced, taking control of a military base on the city outskirts.

A source in Aden told IBTimes UK that a member of the president's national guard had confirmed that Hadi had left for Saudi Arabia.

But other unnamed officials told Reuters that Hadi was still in the country.

The Houthis - a northern tribe which took control of Sana'a in January and put Hadi under house arrest - took Yemen's third city of Taiz earlier this week, but analysts suggested that they would be reluctant to push too far out of their northern heartland into the south.

But on Wednesday the rebel's TV channel reported that it had seized Al-Anad air base, close to Aden.

And the Houthi rebels have now put a bounty of $100,000 on Hadi's head as they push further south.

The news has provoked pandemonium in Aden, according to residents of the city, one of which told IBTimes UK that residents were terrified of what may happen over the next few hours.

"All foreign diplomatic missions in Aden have left the city via private jets. All offices are closed, there are traffic jams - it is chaos right now in Aden," said Murad Abdu, a resident of the southern city. "People are frightened."

Others suggested that residents were calmly resigned to a Houthi invasion of the city.

President Hadi yesterday pleaded for help from the UN Security Council to prevent the northern Houthi rebels from taking control of all of Yemen, while his defence minister asked the countries of the Gulf Co-operation Council (GCC) - which includes Saudi Arabia - to wade in.

Saudi Arabia has massed troops on the border and said that it will act to prevent Iran from arming the Houthis, but has so far refrained from active involvement in the conflict.

The involvement of the two powers has raised fears of a proxy war between Saudi Arabia and Iran, which openly backs the Shia Houthis.