MANILA, Philippines (AP) — The Philippine president says the leadership of the Islamic State-linked militants who laid siege on southern Marawi city remains largely intact despite nearly two months of military offensive and has funded diversionary bombing plots targeting key cities in the region.

President Rodrigo Duterte said in a letter to Congress that despite troops regaining control of much of Marawi and the killings of hundreds of militants "the rebellion persists and a lot more remains to be done to completely quell the same."

The letter aims to convince lawmakers to approve an extension of Duterte's martial law declaration in the south. A copy was seen by reporters Thursday.

The military says about "90 terrorists" have managed to escape from Marawi among the 600 fighters involved.