South Korean activists have sent another batch of propaganda leaflets across the border into North Korea, ignoring calls from the South Korean government to stop the airdrops which it says are inflaming already tense relations on the peninsula.

Activists said the latest batch of 100,000 plastic-covered leaflets was carried across the heavily-fortified border by unmanned helium balloons on Thursday.

They said the leaflets carried messages criticising the government of Kim Jong-il, the North Korean leader, and calling on North Koreans to rise up against him.

The South Korean government has urged the activists to stop sending the leaflets, saying they risk damaging already frayed relations with the North.

The leaflet drops are thought to have been a factor behind North Korea's announcement last week that it would close the frontier between North and South from December 1.

The announcement came after North Korean military officials protested to their South Korean counterparts over the leaflets.

South Korean officials have previously said there is nothing they can do to stop the activists, citing freedom of speech.

However, earlier this week officials at the South Korean unification ministry said they were looking at any possible legal avenues through which they could enforce a ban on the airdrops.