Sierra Leone arrested eight Guineans, including military personnel and fisheries inspectors, whom it accused of carrying out a pirate attack on two locally licensed fishing vessels, officials said on Monday.
But Guinean authorities rejected the piracy charge, saying the men were on a legitimate fisheries protection patrol.
British-trained Sierra Leone naval officers interrupted what they portrayed as a high-seas hold-up by armed men in two launches on Sunday, 18 nautical miles off Freetown inside the West African state's 200-mile (320-km) economic exclusion zone.
They said one of the attacking speedboats escaped north towards Guinea, while the other was seized. The eight men arrested were found with AK-47 automatic rifles and bags of fish, including high-value snapper, taken off the Sierra Leone-licensed vessels.
"They are all Guinean pirates," said Daniel Mansaray, commander of the Sierra Leone Armed Forces Maritime Wing.
He said the men arrested included two lieutenants of the Guinean armed forces -- one from the navy, another from the army -- and two fisheries inspectors.
Guinea's navy said the military personnel were accompanying inspectors from the country's National Fisheries Surveillance Centre (CNSP) on an official patrol.
"You can't talk about piracy," Guinean navy operations commander Mohamed Camara said. But he did not explain what the Guineans were doing in Sierra Leone's economic exclusion zone.
Sean Brady, a British Royal Navy commander who advises the Sierra Leone Maritime Wing as part of a UK training mission for the country's armed forces, confirmed the arrests.
"There was one boat with the pirates and one boat to take away all the bounty to Conakry. ... It's embarrassing for Guinea," he told Reuters.
International law enforcement officials say Guinea's port capital of Conakry on the former French colony's Atlantic coast is a major staging post and jump-off point for criminal gangs trafficking illegal migrants and drugs bound for Europe.
Piracy and illegal fishing are also rife off the West African coastline, a jigsaw of deltas, swamps, mangrove creeks and islands which are poorly patrolled by regional states.
"Sierra Leone waters are pirated all the time and usually they (the pirates) commandeer the catch (of fishing vessels) and take it to Guinea. The fisherman are scared," Mansaray said.
"They are getting too bold -- coming right down the coast to pirate and loot these vessels and stealing millions. If it continues, it will discourage people from licensing their vessels here in Sierra Leone," he added.
The high-seas incident followed a brief visit to Conakry on Friday by newly elected Sierra Leone President Ernest Bai Koroma, who was making his first foreign trip as head of state.
Aides said Koroma had asked Guinean President Lansana Conte and the leaders of Liberia and Burkina Faso for more cooperation to preserve security in a volatile, crime-ridden region that was racked by civil wars for more than a decade.
Sierra Leone has only four maritime patrol vessels and two are out of service due to missing parts. The country's single ocean-going patrol vessel was donated by China.