SEOUL (REUTERS) - Rattled by rising tensions with North Korea, South Korea is taking extra measures to try to ensure the safety of the 2018 Winter Games, including setting up a crack cyber defence team and doubling the number of troops, according to officials and documents reviewed by Reuters.

The Games take place next February in the mountainous resort town of Pyeongchang, just 80km from the heavily fortified border with North Korea.

They come after a series of missile and nuclear tests show the North making rapid advances in its weapons programme and as inflammatory rhetoric between Pyongyang and Washington stirs up concerns about another conflict on the Korean peninsula.

South Korea's Defence Ministry will deploy some 5,000 armed forces personnel at the Games, double the 2,400 on duty during the 2002 World Cup, which South Korea co-hosted with Japan, according to government officials and documents reviewed by Reuters.

Pyeongchang's organising committee for the 2018 Games (POCOG) is also selecting a private cyber security company to guard against a hacking attack from the North, tender documents show.

The committee is seeking to fast-track the selection as tensions rise in the wake of South Korea's controversial deployment of the US Thaad anti-missile system, and as North Korean leader Kim Jong Un tests weapons at an unprecedented rate.

"Cyber threats have increased due to external factors such as the Thaad deployment and recent North Korean missile launches," the committee said in the document.

South Korea has blamed the North for a series of hacking attempts in the last few years, including a 2013 cyber attack against South Korean banks and broadcasters that froze computer systems for more than a week. Pyongyang denied any responsibility.

THREATS INCREASE

While South Korea faces unique challenges with its hostile and nuclear-armed neighbour, the level of threats and security to counter them have escalated globally since South Korea last hosted a major international sporting event.

The POCOG is hiring a private security contractor, stipulating the firm should be capable of running around 500 personnel to operate X-ray screening each day during the event, a separate document seen by Reuters shows.

It has earmarked 20 billion won (S$24 million) for the screening security measures and another 1.3 billion won for the cyber security protection, according to the documents.

An official from the National Intelligence Service, South Korea's spy agency, is in charge of security operations, working with the government's anti-terrorism centre, the organising committee's spokesman told Reuters.

South Korea has also created a new Special Weapons and Tactics team to guard against terrorism around the Games, Asia's first Winter Olympics outside Japan.

"We will search Olympic venues to check for bombs, protect athletes and visitors, and guard against any attempts to assassinate key figures," police inspector Jin Jeong Hyeon from the SWAT team told Reuters.

In late August, the POCOG held a two-day briefing with major Olympic sponsors including McDonald's Corp and Coca-Cola Co to talk about the measures being put in place, according to a government statement. It gave them a look at emergency evacuation facilities during the briefing, though further details were not disclosed.

PAST AGGRESSIONS

While some observers view Pyongyang's threats as bluster, others point to instances of North Korean aggression during the 2002 World Cup and ahead of the 1988 Seoul Olympics as reasons to be concerned.

In June 2002, as South Korea prepared to play Turkey in the playoff for third place at the World Cup, North Korean patrol boats crossed the disputed maritime border and exchanged fire with South Korean vessels, killing six South Korean sailors.

In November 1987, just nine months before South Korea was set to host the Summer Games in Seoul, North Korean agents detonated a bomb on Korean Air Flight 858, killing all 104 passengers and 11 crew.

One of the agents later told investigators the order had come from then North Korean leader Kim Jong Il and one of the aims had been to frighten international athletes and visitors from attending the Seoul Olympics.

South Korea's Sports Minister Do Jong Whan said this week that Seoul was "very concerned about aggressive remarks" traded between Pyongyang and Washington but did not believe Mr Kim would risk a war against countries participating at the Olympics.

The International Olympics Committee is encouraging the participation of North Koreans as athletes, judges or "wild cards" to help ensure the safety of the Olympics, Minister Do added.

North Korea IOC member Chang Ung said earlier this month that the Pyeongchang Olympics will not be affected by the escalating crisis on the peninsula and North Korea will hopefully be able to send athletes.

Despite the heightened security measures, there is not a lot South Korea can do to reassure participants, said former foreign affairs presidential secretary Lee Soo Hyuck. "This issue is more about whether North Korea would decide to carry out hostile actions or not."