FILE - An aerial view of the oil hub city Port Harcourt in Nigeria's Delta region, Aug. 1, 2018.
FILE - An aerial view of the oil hub city Port Harcourt in Nigeria's Delta region, Aug. 1, 2018.

Nigerian authorities said Monday they were looking for 12 sailors from a Swiss-registered cargo ship kidnapped by pirates over the weekend.

The MV Glarus was attacked Saturday near the city of Port Harcourt on its way from Lagos. Shipowner Massoel Shipping said the pirates used long ladders, cutting through razor wire to capture a dozen sailors from the crew of 19.

The Nigerian Maritime Administration and Safety Agency said it had commenced a search-and-rescue operation in coordination with the Nigerian navy and other security agencies, and that it would negotiate for the "unconditional release" of the captives.

Massoel Shipping said it would not disclose the identities or nationalities of the missing crew members for their safety, but the Slovenian foreign ministry said Monday that one of its citizens was among those taken.

Kidnapping is common in Nigeria, and increasingly so in the Gulf of Guinea, where the Swiss vessel was attacked.

There were six kidnappings of crews at sea in the first half of 2018, according to the International Maritime Bureau, all in the Gulf of Guinea.