Soldiers of the Philippines conduct patrol in Mindanao after the martial law was imposed on May 24. (Source: EPA/VNA)

Hanoi (VNA) – The Philippine army with support of helicopters and armoured tanks launched a raid on Islamist militants inside the southern city of Marawi on May 25.

The move came after President Rodrigo Duterte declared martial law in Mindanao to address violence caused by Islamic militants who pledged allegiance with the self-claimed Islamic State (IS).

Philippine authorities said ending violence on the island was difficult as Islamic militants were hiding in residential buildings, had planted improvised bombs in the streets and had taken several hostages.

According to some Philippine military officials, there were about 50-100 Islamic gunmen on the island. A local bishop said that between 12 and 15 Catholic hostages were abducted by the militants.

The violence in the city erupted on May 23 after the army raided the hideout of Isnilon Hapilon, a commander of the Abu Sayyaf group and leader of a branch of IS in the country.

Five soldiers, one police officer and 13 gunmen were killed in the clashes.

The city of Marawi has about 200,000 people, but many residents evacuated due to recent unrest.

Meanwhile, Philippine Secretary of Finance Carlos Domimguez on May 25 affirmed the martial law in Mindanao would not affect business activities and investment on the island.-VNA