Undeterred by an alleged North Korean plot to assassinate him, a South Korean activist Thursday launched leaflets across the tense border calling for the overthrow of Pyongyang's leader Kim Jong-Il.

Park Sang-Hak said he and fellow campaigners launched some 200,000 leaflets slung under large helium-filled balloons from a hilltop in Gimpo, a western suburb of Seoul.

Early this month Park said he was the target of a would-be North Korean assassin sent in response to the leaflet launches, which infuriate Pyongyang.

The North's agent, posing as a defector, was arrested early this month after being tracked down by the South's intelligence agency, according to Park himself and a news report.

The agent was in possession of a poison-tipped needle and other weapons at the time of his arrest, Yonhap news agency said.

Prosecutors said Park was questioned this week over the case.

"He has been questioned, but we cannot disclose details because our investigation was not completed," a spokeswoman for the Supreme Prosecutors Office told AFP.

Park, himself a former defector, vowed to continue the leaflet launches.

"My mission is always risky but I will never give up under the threat of their dirty plot," he told AFP.

Timing devices were attached to scatter the bundles of leaflets when the balloons reach the North. The balloons also carried one-dollar bills, an incentive for North Koreans to overcome fears of punishment and pick up the flyers.

Park, an outspoken critic of the North's communist regime, regularly sends leaflets across the border, sparking angry protests from Pyongyang which has threatened to open fire to halt what it calls a smear campaign.

He said he would launch leaflets again on October 10 when the regime celebrates the 66th anniversary of its ruling party.

There has so far been no official confirmation of the assassination bid, with the intelligence agency refusing comment. But North Korea has a history of trying to silence critics in the South.

In January a court jailed a North Korean spy for 10 years for plotting to assassinate Hwang Jang-Yop, the highest-ranking defector ever to flee to the South.

In July last year, two other North Korean spies were sentenced to 10 years in prison for plotting to murder Hwang, who died of natural causes at his closely guarded Seoul home last year at the age of 87.

In 1997 Lee Han-Young, a nephew of Sung Hye-Rim -- the deceased first wife of North Korean leader Kim -- was shot dead outside his apartment in South Korea.