Pirates ransacked and "effectively hijacked" a merchant ship in the Gulf of Guinea last week, according to maritime security consultancy Gray Page.
The company said in an alert Monday morning that the pirates were armed with grenade launchers and rifles. They stole cash and valuables from the crew and stayed aboard for four days, until a Spanish Navy patrol vessel approached after observing it acting erratically.
"Pirates operating out of West Africa have made the Gulf of Guinea one of the world’s most dangerous sea areas for merchant shipping," the alert read. "Crews should exercise extreme caution throughout the Gulf of Guinea.
"They should avoid slow steaming and watch for the approach of small vessels, especially at night."
Piracy spiked in 2018 after back-to-back annual declines. In the first quarter of 2019, the number of incidents dropped from 66 to 38 year-over-year, the International Maritime Bureau reported.
However, the bureau has also noted concerns about the underreporting of incidents in the Gulf of Guinea, which saw 25 seafarers kidnapped in the first 10 weeks of the year and remains the highest risk area in global trade.
The pirates fled after the Spanish ship, the P-71 Serviola approached, Gray Page said.
The ship's captain reportedly told navy officers that the pirates had prevented him from making radio contact. The automatic identification system had been turned off.
The crew was unharmed.
The Serviola is in the Gulf of Guinea as part of Spain's Defense Diplomacy Plan to prevent conflict and enhance security with partner countries. The ship is currently in the second stage of a three-part, four-month deployment in which it is supporting military operations in the gulf alongside littoral states.