South Korea's military has suspended the launch by balloon of anti-Pyongyang leaflets into North Korea as part of efforts to improve tense cross-border relations, according to a report.

The military has not launched leaflets for a few months now, a military source told Yonhap news agency on Tuesday.

"I understand the decision was made after taking into account the political situation, including the government's efforts to improve inter-Korean ties," the source said.

The defence ministry had no comment. It routinely refuses to discuss military propaganda activities.

After an 11-year moratorium, the South's military resumed floating the leaflets across the border in November 2010, in response to the North's deadly shelling of a South Korean border island that month, Yonhap said.

Defectors and private South Korean activists also stage their own launches of gas-filled balloons, which carry bundles of tens of thousands of leaflets.

These have typically carried news of the Arab uprisings, and call for the overthrow of Pyongyang's leader Kim Jong-Il.

The North, which tightly controls news from outside, has responded angrily to the leaflet launches and has threatened to fire across the heavily fortified border to stop them.

Inter-Korean relations have been frosty since the current conservative government took office in Seoul in February 2008.

They turned icy when the South accused the North of sinking a warship near the disputed border and killing 46 sailors in March 2010.

But in recent months there have been signs of a thaw.

The South replaced its hardline minister in charge of cross-border relations and allowed religious leaders and aid groups to visit the North.

Last week it announced it was resuming medical aid to its neighbour through the United Nations health agency.