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PYEONGCHANG, South Korea — Security here is a top concern for officials just days before the Olympic Games — which are taking place as nuclear tensions have ramped up on the Korean Peninsula.

The Winter Olympics are set to begin on Friday and intense security drills are playing out across the country. It's not just Olympic venues that are possible targets, with tactical teams are ready at airports, subways, even shopping centers.

About 100,000 spectators and several thousand athletes are expected to funnel into PyeongChang for the Olympic Games daily.

Lee Chul-Sung, the commissioner of the national police agency, told NBC News through a translator they've prepared for more than a year so that the games will be peaceful. Police forces were preparing for the gamut of potential terrorist attacks, including cyber terrorism.

In order to prepare for the massive security challenges, about 60,000 forces — including 50,000 military personnel — will “work during the PyeongChang Winter Olympics to ensure its safety," a South Korean government official told NBC News.

There were also several thousand hidden underground shelters in the event of an attack, the official said.

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South Korean soldiers move at a security checkpoint as they replace security guards showing symptoms of the norovirus at the Gangneung Ice Arena in Gangneung on Feb. 6. Jung Yeon-Je / AFP - Getty Images

South Korea has been conducting a series of simulated security drills amidst anxiety over the series of missile tests by North Korea.North Korea agreed to send a delegation of officials and athlete's to the Games last month, after the first high-level talks between the countries in more than two years.

Elizabeth McAleer, with the State Department's Diplomatic Security Service, said “if the US government didn’t deem these games to be safe, we wouldn’t be here right now.”

“The host government and local law enforcement and military have done a great job in putting security levels — around each venue and people should feel safe,” she said.

Special agent Kevin Williams, one of 100 U.S. State Department security agents in South Korea to protect more than 200 U.S. athletes and the tens of thousands American spectators expected, said agents were prepared and he believed the Games would be safe.

Related: PyeongChang braces for frigid weather ahead of Olympics

"We always have contingency plans, ranging from everything small — fire in a venue could be one thing — all the way up to more extreme scenarios,” he said.

Police officers walk the perimeter of the Gangneung Ice Arena in Gangneung, South Korea, on Feb. 5. Paul Chiasson / The Canadian Press via AP

“It is the biggest sporting event on the globe especially right now, especially with all the fans coming in from different countries,” Williams said. “It adds another element of uncertainty as to what could possibly happen to the athletes or to the fans or to the public in general.”

On Tuesday, 900 military personnel were deployed by South Korean authorities to the PyeongChang Olympics after security forces were depleted by a norovirus outbreak, according to The Associated Press.

“To address the shortfall in security workforce due to the isolation, 900 military personnel have been deployed to take over the work of the civil safety personnel,” the Games’ organizing committee said in a statement. “They will work across 20 venues until all affected workforce are able to return to duty.”

More than 30 workers were being treated for the virus in quarantine and 1,200 people working security were being kept in their rooms while being tested for norovirus, according to the AP.

International Olympic Committee previously said in a statement to CNBC that no one has expressed doubts on security.

"We have been in contact with local and international authorities and, in none of the discussions, has anybody expressed any doubt about the Olympic Winter Games Pyeongchang," the International Olympic Committee said in the statement.