MANILA — Thousands of people in the path of a powerful typhoon began evacuating their homes in the northern Philippines on Thursday as officials scrambled to prepare for what could be a devastating storm.

Typhoon Mangkhut, with winds measuring up to 173 miles an hour, is expected to make landfall on Saturday in northern Luzon, the country’s largest and most populous island. The region is home to four million people.

The Philippines’ civil defense chief, Ricardo Jalad, briefed top officials, including President Rodrigo Duterte, and said that government agencies were positioning emergency response teams, food, equipment and medical supplies in the areas likely to be affected.