Islamic insurgents looted cash, gold and jewelry worth tens of millions of dollars when they occupied a southern Philippines town last year, treasure one of their leaders has used to recruit around 250 fighters for fresh attacks.

The military said Humam Abdul Najib escaped from the city of Marawi, which the militants had hoped to establish as a stronghold for Islamic State in Southeast Asia, before it was recaptured by the military in October after five months of ferocious battles and aerial bombardment.

Since then, Najib, also known as Abu Dar, has used the booty looted from bank vaults, shops and homes in Marawi to win over boys and young men in the impoverished southern province of Lanao del Sur, military officers in the area said. Hardened mercenaries are also joining, lured by the promise of money.