Armed gunmen had kidnapped the eight members of the Happy Lady tanker crew on New Year's Eve. A Greek official said the group of eight was released after "the successful end of negotiations."
Armed hostage-takers on Wednesday released a Greek oil tanker captain and seven crew members.
The crew members of the Greek-flagged Happy Lady tanker were kidnapped on December 31 in the port of Limbe near Cameroon's economic capital Douala. The crew members comprised five Greeks, two Filipinos and one Ukrainian national.
"I am delighted with the release of five Greek sailors," said Greek Merchant Marine Minister Giannis Plakiotakis. "Our coordinated efforts have been effective."
Plakiotakis noted that the sailors were only released after "the successful end of negotiations."
Global epicenter of piracy
Over the past two years, the Gulf of Guinea -- which stretches more than 5,700 kilometers (3,500 miles) from Senegal to Angola -- has become the global epicenter of maritime piracy.
In 2018, more than 170 incidents of piracy and armed robbery of tankers and merchant vessels were reported, according to figures provided by the International Maritime Bureau (IMB).
The coast off of Nigeria is considered one of the most dangerous points, with the IMB saying "all waters in (and) off Nigeria remain risky.
"In many past incidents, pirates have hijacked vessels for several days and ransacked the vessels and stole part cargo, usually gas oil," the IMB said on its website. "Vessels are advised to be vigilant."