SEOUL - A South Korean court on Thursday passed 10-year prison sentences on two North Korean agents who posed as fugitives from the communist state in a bid to assassinate a top-ranking defector.

"The defendants admit all the charges, and testimony from other defectors and former agents verified their statements" about their identities and mission, said senior judge Cho Han-Chang.

"Had the defendants succeeded in taking root here, they would have posed a very serious threat to Hwang`s life."

The agents, handcuffed and wearing khaki prison outfits, appeared calm when the sentences were read out.

North Korea has denied involvement in the bid to assassinate Hwang Jang-Yop, accusing Seoul of inventing the story to fuel tensions between the neighbours.

Hwang, architect of the Pyongyang regime`s ideology of "juche" or self-reliance, was once secretary of the ruling Workers` Party and a tutor to current leader Kim Jong-Il.

He defected in 1997 during a visit to Beijing, becoming the highest-ranking official to flee the hardline state, and now lives under guard in the South at a secret address.

The judge said Hwang`s defection symbolised the supremacy of the South`s system over the communist North and his assassination would have damaged the country`s democratic order.

The pair, both aged 36 and identified as Kim Myong-Ho and Tong Myong-Kwan, joined the North`s communist party in 1998 and were selected as agents in 2004.

In November 2009 the two army majors received orders directly from the North`s military intelligence head Kim Yong-Chol to kill Hwang, the court said.

The pair arrived in South Korea in January this year in the guise of defectors. But their fake IDs were revealed during routine questioning by intelligence authorities soon afterwards.

Prosecutors said fabrications about their birthplaces, home towns and educational background came to light through cross-examination and from testimony by genuine defectors.

Prosecutors had requested 15-year terms.

Judge Cho, citing mitigating circumstances, said the defendants were born in a communist country and selected for training as agents, thus "had no choice but to follow orders".

"After their real identities were exposed, the defendants admitted they were agents and began cooperating with the investigation," the judge said.

"Hoping that the defendants will accept and endorse the (South`s) free democratic system and settle down here when they complete serving prison terms, the court orders 10 years in prison for each of the defendants."

Despite the North`s denials of involvement in the assassination plot, its official website Uriminzokkiri on April 5 threatened Hwang with death over his criticism of the Pyongyang regime during trips to the United States and Japan.

Hwang, now 87, "will not be safe anywhere", the website warned. "You must not forget traitors have always been slaughtered with knives."

Three days after Hwang`s defection in 1997, another high-profile defector was assassinated in Seoul.

Lee Han-Young, a nephew of Sung Hye-Rim -- the deceased first wife of North Korean leader Kim Jong-Il -- was shot dead outside his apartment.

Lee had lived in the South for 15 years. He was murdered after breaking his long silence about Kim`s private life.

Tensions are currently high on the Korean peninsula after the South accused the North of torpeding one of its warships in March with the death of 46 sailors.

BDST: 13:08 HRS, 1 July, 2010