Four provinces of Yemen's formerly independent south, including its main city Aden, said Thursday they would defy all military orders from Sanaa after President Abdrabuh Mansur Hadi resigned.

The committee in charge of military and security affairs for Aden, Abyan, Lahej and Daleh, which is loyal to Hadi, said it had taken the decision after the president, who originally hails from the south, stepped following a deadly standoff with militia in control of the capital.

The committee placed police and troops on alert across the four provinces.

It instructed them to take orders only from the provincial governors and the fourth military region command in Aden, whose officers are Hadi loyalists.

It condemned the "tragic events in Sanaa and the totally unacceptable demands made by the Huthis," the Shiite militiamen who have controlled much of the capital since September.

The formerly independent south has three other provinces further east -- Shabwa, Hadramawt and Mahra.