Days after a historic inter-Korean summit Lee Min-bok, a defector who has been flying anti-Pyongyang leaflets into the North for 15 years, received a call from an official at Seoul's Unification Ministry urging him to halt his balloon campaign.

It was a plea by South Korea not to jeopardise the recent thaw, engineered by the leaders of the two Koreas who agreed during last week's summit to cease all hostile acts along the border - including the distribution of leaflets - from May 1.

On Saturday, police prevented a planned release of balloons by a defector group after a confrontation with anti-leaflet protesters.

For Lee, the campaign is personal. He says reading such leaflets as a young man in the North brought an "awakening moment" in 1990 that helped him realise how oppressive and destitute his homeland was at a time when the South was emerging as an economic powerhouse. In 1995, he escaped to South Korea.

"I really believed that Kim Il Sung was the centre of the world and he was making everything right and great for us," Lee said, referring to North Korea's founding father, the grandfather of current leader Kim Jong Un.

"Realising what I had learned, heard and read were all lies, I decided to defect to the South to live with the truth."