(CNN) On the first day of Japan's return to commercial whaling, two whales were killed and brought back to port.

The two minke whales that were harpooned are the first to be killed by Japan for commercial purposes in more than 30 years.

Commercial whaling was banned in a 1986 International Whaling Commission moratorium. However, Japan withdrew from the International Whaling Commission in December and resumed commercial hunting in its territorial waters and economic zone despite international outcry.

A fleet of five whaling boats departed the northern port of Kushiro on Monday. A separate deep-water fleet was scheduled to leave from the southern port of Shimonoseki the same day.

A captured minke whale is unloaded from a ship in Kushiro, Japan, on Monday.

The Japanese Fisheries Agency published quotas on Monday for the next six months of commercial whaling. Officials insist that they will engage in sustainable practices.

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