US top diplomat Kerry in Seoul after North Korea's muscle flexing

US Secretary of State John Kerry (left) talking to South Korean President Park Geun Hye at the Presidential Blue House in Seoul, South Korea on May 18, 2015. -- PHOTO: EPA
US Secretary of State John Kerry (left) talking to South Korean President Park Geun Hye at the Presidential Blue House in Seoul, South Korea on May 18, 2015. -- PHOTO: EPA

SEOUL (AFP) - US Secretary of State John Kerry is in Seoul on Monday to discuss security issues in the wake of a new ballistic missile test by North Korea and the reported execution of its defence chief.

After meeting with President Park Geun Hye and other senior South Korean officials, Kerry is due to deliver a comprehensive policy speech on cyberspace, which has become another outlet for North Korean belligerence.

In an effort to revive long-stalled denuclearisation talks, Washington has made it clear in recent months that it is open to preliminary discussions with Pyongyang, but that process has been complicated by some significant North Korean military muscle flexing.

Just over a week ago, the North said it had successfully test-fired a submarine-launched ballistic missile (SLBM) - a technology that could eventually offer the nuclear-armed state a survivable second-strike capability.

UN sanctions ban Pyongyang from using ballistic missile technology.

While North Korean leader Kim Jong Un hailed the acquisition of a "world-class strategic weapon," US defence officials sought to play down the test, saying Pyongyang was still in the earliest stages of developing an SLBM capability.

Nevertheless, in Beijing at the weekend, Kerry slammed the North's "destabilising" behaviour as "unacceptable."

Internal stability in North Korea has also become a concern after South Korea's intelligence agency reported last week that Pyongyang's defence minister had been purged and most likely executed.

The agency said it had unverified reports that the execution had been carried out at close range with a high-calibre anti-aircraft gun.

Some observers said the execution, if confirmed, suggested Kim was still struggling to cement his absolute authority in a country that has been ruled by the Kim family dynasty for seven decades.

During his talks with Park and other officials, Kerry is expected to underline US commitment to its military alliance with South Korea, which hosts a permanent deployment of close to 30,000 US troops.

- Denuclearisation talks -

During his visit to Beijing, Kerry had voiced hopes that the successful conclusion of a nuclear deal with Iran would encourage North Korea to resume six-party negotiations on its nuclear programme.

The talks, grouping North and South Korea, Japan, the United States, China and Russia, were aimed at getting North Korea to give up its nuclear weapons in return for economic and diplomatic benefits and security guarantees.

But they have not been held since December 2008.

President Barack Obama's administration has been accused of taking its eye off the ball over North Korea's nuclear programme, while focusing its attention on Iran.

A recent report by US researchers warned that North Korea appeared poised to expand that programme over the next five years and, in a worst case scenario, could possess 100 atomic arms by 2020.

North Korea carried out nuclear tests in 2006, 2009 and 2013, and has an extremely active ballistic missile development programme, although expert opinion is split on how much progress it has made.

Later Monday, Kerry was scheduled to lay out a comprehensive foreign policy speech on the use of cyberspace, including issues of cyber-security.

Seoul has blamed North Korean hackers for a series of devastating cyber-attacks on military institutions, banks, government agencies, TV broadcasters and media websites in recent years.

The United States also blamed the North for a cyber-attack on Sony over its controversial North Korea-themed satirical film "The Interview" last year.

Pyongyang denied involvement in the Sony hack but strongly condemned the film, which features a fictional plot to assassinate leader Kim Jong Un.

South Korea's defence ministry believes North Korea runs an elite cyber-warfare unit with up to 6,000 personnel, and regards its ability to launch hacking attacks as a major security threat.

Last month, President Park appointed an army general to the new post of national cyber-security tsar, specifically tasked with defending against North Korean hacking attacks.