SEOUL - Former North Korean soldiers who have defected to the South formally launched a campaign Thursday to topple the Pyongyang regime with the help of serving soldiers there.

The NK People's Liberation Front simulated the execution of the North's leader Kim Jong-Il at an inauguration ceremony held on the 62nd anniversary of the founding of North Korea.

It was attended by about 100 defectors who pledged to overthrow the regime with the help of military members still in the communist state.

The defectors, who included dozens of women, were clad in military uniforms and chanted "Let's get Kim Jong-Il!" and raised their fists.

They clapped and laughed as a man wearing a Kim Jong-Il mask enacted the North Korean leader being shot dead by a firing squad, rolled into a carpet and taken away.

Hwang Jang-Yop, a former top official who defected to the South in 1997, said in a message read to the group: "Judgment day for Kim Jong-Il is coming."

"We're talking about the world's most despicable criminal group. What's important to bring it down is organised preparation," said Hwang, the architect of North's ideology of "juche," or self-reliance, and once a tutor to Kim.

Hwang, 87, now lives under guard in the South at a secret address.

The group, which claims about 200 members, has vowed to contact soldiers in the North through mobile phones in a campaign to overthrow Kim's dictatorship.

"We need to hit Kim from behind his back," an active North Korean soldier allegedly based in the North's western port of Nampo said in a message read by a group member, adding that the number of people who hate Kim was growing.

The group plans to help smuggle publications, videos and other material into the tightly controlled country and circulate them among the North's soldiers.

South Korea has many organisations representing refugees from the North or campaigning against the regime, but this is the first to link former soldiers.

Around 19,000 North Koreans have fled the North for the South since the end of the 1950-1953 war, the vast majority in recent years.

Despite its ailing economy and severe food shortages, the North's military totals almost 1.2 million members.