DNA tests have confirmed the death of Isil's leader in the Philippines, who in 2017 laid siege to the city of Marawi and was among the group's most senior figures in the region.

Tests carried out by the United States at the Philippines' request found that remains retrieved from a battle on March 14 belonged to Owaida Marohombsar, who was also known by his nom de guerre Abu Dar.

He was one of four terrorists killed during the fierce gun fight near the southern town of Tubaran in Lanao del Sur province.

"This is another milestone in our campaign to finish and defeat ISIS and local terror groups in the country," said the Philippines' interior minister Eduardo Ano.

"For now, his group is leaderless. We are monitoring who will replace Dar," added defense Secretary Delfin Lorenzana at a press conference over the weekend.

Marohombsar helped lead the May 23, 2017, siege of Marawi, which troops quelled after five months of ground assaults and airstrikes that left more than 1,100 people, mostly militants, dead and destroyed the mosque-studded city's commercial and residential districts.