A Ukrainian ship laden with tanks and freed by Somali pirates after a five-month hijack approached port in Kenya on Thursday with debate still ranging over ownership of the sensitive military cargo.

In one of the highest-profile seizures of recent times, pirates captured the MV Faina in September with its 20-man crew and a cargo of 33 Soviet-era T-72 tanks plus other weapons.

A regional maritime group based in Kenya's Mombasa port, and foreign diplomats, have said the arms were destined for southern Sudan -- a possible embarrassment for Kenya, which helped broker a 2005 peace deal there.

But Kenyan and Ukrainian officials waiting for the ship on Thursday again denied that.

"The cargo that the Faina is carrying was purchased from the Ukrainian government by the Kenyan government," Kenya's deputy defence minister David Musila told reporters after meeting the Ukrainian delegation in Kenya to greet the freed sailors.

"This is our cargo."

The head of Ukraine's foreign intelligence service, Mykola Malomuzh, backed that up. "The cargo is being shipped in legal fashion to Kenya for the Kenyan armed forces," he said.

"We hereby reject all accusations suggesting that the cargo is being shipped to other countries."

The Faina's crew were due to undergo medical checks on arrival. Various of them have been ill, and the Russian captain died, apparently of sickness, in the first days of the saga.

The Somali pirates released the Faina last week after taking a ransom of $3.2 million, according to regional maritime sources and members of the gang themselves.

The ship's manifest, seen by Reuters, lists Kenya as the "consignee" but gives MOD/GOSS as the contract reference.

GOSS is an abbreviation widely used around Africa for Government of South Sudan. But Nairobi has said in this context it stood for "General Ordinance Supplies and Security", a department of Kenya's defence ministry.

"Kenya has to save face here," a European diplomat said.

"They will deliver the equipment to their military with great fanfare and in front of all the cameras, then when noone's looking, a year or so down the line, off it will go to Sudan."