North Korea has sent a protest letter to South Korea's presidential office demanding that South Koreans stop floating anti-Pyongyang propaganda leaflets into its territory.

A government official in Seoul said Tuesday that the North's National Defense Commission (NDC) sent two messages to the National Security Council on Saturday and Monday.

The official said that the North said in the messages that South Korea should first stop sending propaganda leaflets before proposing high-level inter-Korean talks.

The North is known to have said in the messages that military retaliation could follow if such leaflets continue to be sent to the North. 

The presidential office is known to have sent a reply on Sunday to the NDC to stress that Seoul is duly abiding by a February inter-Korean agreement to halt all acts of provocation and slander, but the South Korean government cannot restrict people's freedom of assembly without legal basis. 

The official said that the government will not take any action regarding the latest massage that arrived on Monday, as the North is only repeating its previous demand.