MANILA -- (UPDATE) Twenty people died in the Cordillera region, mostly due to landslides, authorities said Sunday, as they accounted for damage wrought by Typhoon Ompong (Mangkhut).

Seven people died in Benguet, 6 each in Mountain Province and Baguio City, and 1 in Kalinga province, according to a report from Philippine National Police-Cordillera.

Baguio Mayor Mauricio Domogan also reported 6 casualties in his city in an interview on DZMM. Three others were missing, he said.

The remains of the 6 were pulled from debris in the mountain resort city, he said.

Domogan blamed the landslides on clogged drainage systems, which caused the soil to soften.

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"Nag prepare kami pero wala ka magawa sa landslide. Unexpected na mag landslide. Ito yung problema," Domogan told radio DZMM.

(We prepared but you can't do anything during a landslide. The landslides were unexpected, that's the problem.)

Ompong smashed through northern Luzon Saturday, triggering floods and landslides in the area.

• IN PHOTOS: Ompong's trail of destruction

In the Cordillera region alone, several roads were impassable due to flooding and landslides, these are: Kennon Road, Marcos Highway, Baguio-Bontoc Road, and Benguet-Nueva Vizcaya.

• LIST: Closed roads in northern Luzon due to Ompong