Between 40-50 Arab special forces soldiers arrived in Aden on Sunday and deployed alongside local fighters against the Houthi militia, a spokesman for the Southern Popular Resistance said.
The forces were engaged in fighting in the area around Aden airport, spokesman Ali al-Ahmed said.
The Saudi-led coalition against the Houthis has denied reports it has started a ground offensive in Aden but has refused comment on the possibility of special forces being involved.