SEOUL -?The Republic of Korea(ROK)?has stepped up security efforts to ensure a successful and smooth Nuclear Security Summit in Seoul.

The second Nuclear Security Summit to be held on March 26-27 will be the largest global event South Korea has ever hosted, getting together leaders from 53 countries and four international organizations.

South Korean police have been put on the highest level of alert to counter threat of terrorism and street riots.

"The police agency, based on the success of the Seoul G20 Summit 2010, will work closely with local security departments. We will drill on protective services, countermeasures against illegal demonstrations, and traffic management to make sure that the nuclear security summit will go smoothly," Cho Hyun-oh, commissioner of the National Police Agency (NPA), told a news conference earlier this month.

About 36,000 police officers will be deployed around the COEX convention center in southern Seoul, the main venue of the summit, leaving nothing to chance.

Seoul's airspace will buzz with security helicopters, while latest guard boats with underwater monitoring equipment will patrol the Han River.

The summit venue will be surrounded by a three-layer security barrier starting Sunday to restrict public access and prohibit illegal rallies from disrupting the event.

Security has also been stepped up around subway stations and other points vulnerable to terrorist attacks. ?

Earlier this month, police opened a situation room equipped with high-tech devices to monitor the summit venue and manage general security operations.

The situation room has access to more than 2,000 close circuit cameras around the venue and is also capable of monitoring the location of patrol cars and police units deployed in the area.

There will be road closures around the summit venue, buses will deviate from their daily routes, a subway stop close to the convention center will be closed, and police are set to establish checkpoints around the venue.

Police have asked for active cooperation of the public in reducing traffic congestion by encouraging them to leave their cars at home and use public transportation during the summit.

South Korean armed forces have also been placed on their highest level of military preparedness for the summit.

"I urge all soldiers to be armed with perfect military readiness and security operation readiness to guarantee the success of the Nuclear Security Summit,"said Defense Minister Kim Kwan-jin in a recent meeting with top military commanders.