Mikhail Voitenko of the Sovfracht Maritime Bulletin said citing foreign media that the pirates had been paid $3.2 million and promised to release the vessel after checking and dividing the money.
"The first group of pirates left the vessel this morning after receiving their cut," said Voitenko, who spoke to the Faina's owner early Thursday.
Voitenko said the pirates were most likely to leave in groups, one after another. "There are approximately 80 pirates on board the Faina," he added.
"After the last pirate leaves, a U.S. warship will approach the Faina to provide fresh water, food and medical assistance if required and subsequently accompany the vessel to Mombasa," Voitenko said.
He said the vessel would unload its cargo of tanks and weapons at the Kenyan port.
The Faina, with a crew of 17 Ukrainians, three Russians and one Latvian, was hijacked off the Horn of Africa on September 25. The vessel's Russian captain died of a heart attack in the early days of the hijacking. The pirates initially demanded a $35 million ransom for the vessel, which was carrying tanks and weapons.
Some media claimed that the intended destination for the weapons was southern Sudan's rebel Dafur region, and not Kenya as was announced. Both the Ukrainian and Kenyan authorities have denied the claims.
According to the UN, Somali pirates carried out at least 120 attacks on ships in 2008, resulting in a yield of around $150 million.
Up to 20 warships from the navies of at least 10 countries, including Russia, are involved in anti-piracy operations in the area off Somalia which has no coast guard or navy and has had no functioning government following 15 years of civil war.