Three North Korean cargo ships have begun loading fertilizer at South Korean ports.

One of the freighters, the Baekdusan, arrived in Ulsan on the southeastern coast late Sunday. The other two vessels arrived at Gunsan on the southwestern coast and Yeosu on the south coast early Monday morning.

It is the first time for a North Korean ship to enter a South Korean port since the North delivered relief materials to the South in the wake of a devastating typhoon 21 years ago.

The North Korean cargo ships are scheduled to head back to the North around Thursday with 83-thousand tons of fertilizer. The shipment is part of the 200-thousand tons of fertilizer Seoul had agreed to donate to the North during vice-ministerial talks last week.

Ten thousand tons will be delivered to the North overland through the inter-Korean border, with the first batch already sent on Saturday.

The North Korean vessels crossed the inter-Korean sea border into South Korean waters in accordance with their mutual maritime agreement instead of making a long detour through international waters.