"Subaihi was arrested in the city of Houta" in Lahj province, rebel spokesman Mohammed Abdulsalam said in a statement aired by the militia's Al-Massira television.
Subaihi escaped house arrest under the Huthi rebels in Sanaa this month and joined the president in Aden.
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He had taken charge of organising defence lines as anti-government forces approached.
Abdulsalam said Subaihi and others arrested were "transferred to Sanaa and are held by the armed forces."
Fierce fights took place in Houta between anti-Hadi forces and loyalists as the rebels closed in on Aden.