Philippine President Rodrigo Duterte has said martial law on Mindanao island could last a year, while the army fights against Islamist militants.

The violence on the southern island has left three members of the security forces dead, officials say, the BBC reported on Wednesday.

Duterte earlier declared martial law for 60 days on Mindanao, where Muslim rebel groups are seeking autonomy.

Some of the groups, such as the Maute, have pledged allegiance to Daesh terrorist group.

After announcing martial law on Tuesday, President Duterte, a Mindanao native, warned that he would be harsh in dealing with terrorism.

"If it would take a year to do it, then we'll do it. If it's over within a month, then I would be happy," he said in a video posted online by the government.

Source: MENA