MANILA, May 24 (Xinhua) -- Philippine President Rodrigo Duterte said on Wednesday that he would be harsh in dealing with terrorists in the country.

In an interview posted by Communications Assistant Secretary Mocha Uson on her blog, Duterte said he has decided to cut short his visit to Russia and head home to personally deal with the problem.

"Let me just tell everybody that I have declared martial law in Mindanao," he told Uson on the plane.

"Martial law is martial law. I will be harsh," Duterte said, adding that the martial law he imposed Tuesday night is no different from the one in the 1970s.

He said he has to impose martial law "to preserve the Republic of the Philippines and the Filipino people."

At 10 p.m. local time on Tuesday, Duterte placed the entire Mindanao island, including the island provinces of Basilan, Sulu and Tawi-Tawi in the southern Philippines under martial law after a firefight happened between the government troops and some 100 Maute fighters, a band of loose armed group with alleged link to the Islamic State militants.