The South Korean government declared a state of disaster on Saturday over wildfires that broke out in the country's southeastern areas including Ulsan city, North Gyeongsang province and South Gyeongsang province, the Ministry of the Interior and Safety said.

A mountain fire first broke out in Sancheong County in the province of South Gyeongsang on Friday afternoon before the fire continued to spread on Saturday.

More massive mountain fires erupted on Saturday morning in other parts of the southeastern regions.

Acting President Choi Sang-mok inspected the situation in the affected places, ordered relevant authorities to work together to mobilize all equipment available and bring the wildfires under complete control.

At around 3:30 p.m. local time on the same day, the Korea Forest Service raised the national emergency alert level in the most affected areas to its highest, which is the "severe" stage.

So far, four firefighters were reported dead and six were injured, local media reported.