Pirates kidnapped four Koreans and one Filipino crew member from a tuna-fishing vessel close to Benin in the Gulf of Guinea earlier this week, Ghanaian police said.
The Gulf of Guinea, a key shipping route extending from Senegal to Angola, accounted for the vast majority of maritime crew abductions last year, with pirates targeting commercial vessels.
The Ghana-registered boat was attacked on Monday although the Ghana navy recovered the vessel and rescued some crew members, Felix Charles Asare, crime officer for the Marine Police Unit told AFP late on Wednesday.
"Efforts are under way to rescue the abducted crew members," he said.
"Information we've gathered from the crew members indicate that the pirates took away five other members made up of four Koreans and a Filipino."
He said Ghana's navy had been on the alert in the country's territorial waters as pirates intensified attacks.
Armed pirates kidnapped five other seamen two weeks ago, stealing valuables after holding the crew for six hours before releasing them, he said.
Major international shipping and maritime companies last month called for a coalition to combat piracy in the Gulf of Guinea, includingsignatories from Europe, Japan, China and India.
Several EU nations often have naval vessels in the area, but pirate gangs, mostly Nigerians, are increasingly attacking beyond Nigeria's coastal waters, where they know ships are more vulnerable.
The Gulf of Guinea accounted for more than 95 percent of global maritime kidnappings last year – 130 out of 135 cases, according to the International Maritime Bureau, which monitors security at sea.