The annual college entrance exam kicked off nationwide Thursday with a record number of retakers driven in part by an increase in medical school admissions.

A total of 522,670 students, including high school seniors and graduates, were registered to take the state-administered College Scholastic Ability Test, up 18,082 from last year.

High school seniors numbered 340,777, accounting for 65.2 percent of the total, while graduates numbered 161,784, the largest figure since 2003.

Many of the graduates, or around 93,195 people, were believed to be first-year university students taking another shot at the exam to get into a better school next year, according to Jongro Academy.

The large number of graduates has been attributed to the increase in the medical school quota next year, with 39 medical schools nationwide planning to accept a combined 4,610 students, up 1,497 from this year.

The increase comes after the Yoon Suk Yeol administration decided to add around 2,000 slots per year over the next five years to address a shortage of doctors.

Students were required to arrive at their designated testing sites by 8:10 a.m. to prepare for the Korean language portion of the five-part exam, which began at 8:40 a.m.

The CSAT is one of the nation's most important academic events, as getting into a prestigious university is considered a prerequisite for a good career path down the line.

In keeping with its policy, the government had said extremely difficult "killer" questions would be excluded from this year's exam.

"We made sure the exam could differentiate the levels of students simply using material covered by public education," Choe Joung-chul, a Dongguk University professor and head of the CSAT question-setting committee, said during a press conference.

The test will run from 8:10 a.m. until 5:45 p.m., during which time the authorities will control noise levels outside 1,282 examination sites nationwide.

During the English listening evaluation portion from 1:05 p.m. to 1:30 p.m., all aircraft takeoffs and landings will be prohibited, with the flight schedules of 156 airplanes adjusted during this time.

All aircraft in flight, excluding those in emergency situations, must also remain in the air at an altitude of 3 kilometers or higher, while military exercises causing excessive noise will be temporarily halted.

The Seoul metropolitan government extended morning rush hour subway operations to 6 a.m. to 10 a.m., from the regular 7 a.m. to 9 a.m., to help test-takers get to their test sites on time.

Police also deployed over 10,000 personnel to escort exam papers to and from testing sites and maintain order and stability around schools.

The test results will be delivered to students on Dec. 6. (Yonhap)