North Korea has demanded South Korea to repatriate nine North Koreans who had crossed the inter-Korean maritime border in the Yellow Sea last week.

The Unification Ministry said on Thursday that the North's Red Cross sent a message to the South's counterpart that called for the prompt return of the nine individuals, who are currently being investigated by the South.

North Korea is reportedly asking South Korea to return not only those aboard the boats, but the vessels which carried them as well.

The North Koreans, the families of two brothers, crossed the border on Saturday in two small boats and expressed their intentions to defect to the South. The group totaled three men, two women and four children.

The National Intelligence Service and the South Korean police are currently investigating the North Koreans' motives to leave the communist nation.

In February, 31 North Koreans crossed the maritime border by boat, with 27 returning to the North while four choosing to stay in the South. In this particular case, North Korea consistently demanded the return of all 31 individuals aboard the vessel.