SEOUL - South Korea fell silent Thursday with heavy trucks banned and businesses opening late as more than 600,000 students sat the high-stakes annual college entrance exam that could define their future in the ultra-competitive country.

Success in the exam -- which teenagers spend years preparing for -- means a place in one of the elite colleges seen as key to future career and even marriage prospects.

To clear the roads for the 606,000 students to ensure they arrive on time, government offices, major businesses and even Seoul's stock market opened an hour later than usual at 10:00 am (0100 GMT).

Transport authorities banned all airport landings and take-offs for a 30-minute period in the early afternoon to coincide with the main language listening test.

Work at many construction sites was suspended and large trucks banned from the roads near the test venues.

The exam was taken at 1,183 venues nationwide from about 9:00 am (0000 GMT) to 5:30 pm (0830 GMT).

TV news channels showed nervous-looking students walking into the test venues after tearful hugs with parents, as hundreds of younger students cheered on their senior classmates.

With so much at stake, thousands of parents flocked to temples and churches to pray, with monks and pastors holding special sessions for students.

The pressure to score well in the exam has been blamed for teenage depression and suicide rates that are among the highest in the world.