The move escalated a crisis that threatens to split the Arab world's poorest country between the rebels, known as Houthis, who control the capital Sanaa and much of the north, and Hadi, who appears to be establishing a base in the once-independent south.
The rebel-run state news agency SABA quoted the Houthis' Revolutionary Committee as saying that they are monitoring the "suspicious" activities of Hadi. It did not say whether a formal arrest warrant has been issued.
The group also warned state employees and even diplomatic missions against dealing with Hadi as president, saying they would be "held accountable."
Hadi resigned from the presidency after the rebels placed him under house arrest in Sanaa last month, but retracted the resignation after fleeing to Aden. Since then, he has been holding meetings with tribal leaders, security officials and parliamentarians.
Today he replaced the intelligence and police chiefs in Aden as part of a shake-up to remove supporters of former President Ali Abdullah Saleh, now allied with the Houthis, from key positions, according to security officials. The officials spoke anonymously because they were not authorized to brief the press.
The Houthis yesterday warned Prime Minister Khaled Bahah and his cabinet -- all of whom resigned when Hadi did -- to return to their posts or face arrest.
The ministers have been under house arrest in Sanaa for weeks. Houthi militiamen prevented one minister from fleeing to Aden yesterday.
Abdel-Azizi al-Gobari, the leader of a small anti- corruption party who met with Bahah today, said the Prime Minister would only take orders from Hadi.
