South Korea unveiled independent sanctions on Iran Wednesday for its contentious nuclear program suspected to be a cover for developing nuclear weapons, joining the U.S.-led campaign to punish the country.

Seoul blacklisted 102 entities and 24 individuals believed to be involved in Tehran's nuclear activities, and decided impose a "severe penalty"on the Seoul branch of Bank Mellat, the only Iranian bank in the country suspected of illicit financial transactions aiding the nuclear program.

The previous probe into Bank Mellat by Seoul's financial authorities revealed violations of the Foreign Exchange Transaction Act, the government said. The U.N. accused the bank of having "facilitated hundreds of millions of dollars in transactions to help aid Iran's nuclear, missile, and defense entities."

"Transactions by Bank Mellat that involves only one dollar will still have to gain prior government approval," a government official told reporters after a joint briefing by South Korean officials from government branches and agencies concerned, including the foreign ministry, the Financial Supervisory Service (FSS) and the finance ministry.

Fifteen Iranian banks, including Bank Mellat, the Islamic Revolutionary Guard Corps (IRGC), the Islamic Republic of Iran Shipping Lines (IRISL), have been blacklisted. CISCO Shipping Company and Iran Petrochemical Commercial Company are among other Iranian entities that made their names in Seoul's bad books.

Under Seoul's sanctions, adopted in addition to U.N. sanctions over Tehran's uranium enrichment program that some say is a cover for developing nuclear weapons, all financial institutions here will have to report to the South Korean authorities or gain prior permission if they are to engage in financial transactions worth more than 10,000 Euros with Iran.

Seoul will also step up Iran-related cargo inspections, put blacklisted entities and individuals on travel ban list and limit the country's investment into Iran's gas and oil refinery industries.

The independent sanctions came after the United States ramped up its efforts to push Seoul to join its campaign to foil Iran's alleged nuclear ambition. Robert Einhorn, the State Department's special adviser for nonproliferation and arms control, visited Seoul in August to press the issue.

Officials from Tehran, denying the charge and claiming its nuclear activities are all for peaceful purposes, threatened countermeasures.

Seoul's additional sanctions are meant to prop up global nonproliferation efforts as a "responsible member of the international society,"and the government takes the issue particularly seriously as it is related to nuclear issues of the Democratic People's Republic of Korea, a senior government official told reporters after the joint briefing.

It was the government's own decision to impose the "unilateral" sanctions, and the measures are based on the existing U.N. resolution, he added.

Despite the government's efforts to "minimize damage"the sanctions might bring about, concerns still linger over worsening financial ties with Iran. Seoul relies on Tehran, the biggest trade partner in the Middle East, for 10 percent of its crude oil imports. Some 2,000 small and mid-sized enterprises have tapped into the fast-growing Iranian market.

The government will still maintain legitimate trade relations with Iran, and will take measures to support domestic small and mid-sized firms, foreign ministry spokesman Kim Young-sun told reporters. Seoul's oil imports from Tehran will not be affected by sanctions, another official said.

The European Union, Australia, Canada and Japan have announced separate sanctions against Iran.