From a month earlier, the rate also jumped 1.2 percentage points from 3.8 percent.
The figure marked the highest since January 2010 when it hit 5 percent, while it also recorded a 16-year high among all February figures.
The number of jobless people in February reached an all-time high of 1.35 million on a seasonally adjusted basis, amid an upbeat pace of the number of economically active people in the country.
The number of employed people stood at 25.78 million in February, up 371,000 from a year earlier, the largest on-year gain in six months.
The unemployment rate for young people, aged between 15 and 29, reached 12.3 percent last month, down slightly from a record 12.5 percent tallied a year earlier but up sharply from January's 8.6 percent.
Statistics Korea said the record-high unemployment rate in February came as a great number of college seniors flooded into the job market upon graduation. These people competed in an already tight market with existing young and older job seekers.
"Usually, the unemployment rate rises during the January-February period, which overlaps with the college winter vacation and graduation," said Bin Hyun-joon, head of the agency's employment statistics division.
He pointed out that many young people also applied for civil service exams in mid-February, pushing up the youth jobless rate.
The sluggish performance of the manufacturing sector, which accounts for one-fifth of the country's total hiring, also created a drag on the local job market.
The number of new jobs offered by manufacturing businesses fell by 92,000 in February from a year earlier, extending its losing streak to eight straight months.
Local manufacturers newly hired around 150,000 people every month throughout 2015, with the number peaking at 191,000 in October. But the figure plunged to 20,000 in June last year and posted negative growth the following month for the first time in 49 months as the country had struggled with faltering exports for nearly two years.
"Labor-intensive businesses like shipbuilding are undergoing strict restructuring, and a massive number of workers who lost their jobs poured into the market," said the official. "The downbeat mode of the manufacturing sector is expected to continue further."
Sectors like shipbuilding, shipping and steelmaking have been suffering huge losses stemming from market saturation that hurt new demand and low oil prices.
The finance ministry said the job market will face further downside risks in the coming months.
"Rising uncertainties at home and abroad, contracted domestic demand and ongoing corporate restructuring are weighing heavily on the employment market," said the ministry. "The government will come up with supplementary measures to improve job quality for young people later this month." (Yonhap)
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