Somali pirates holding a ship laden with Russian tanks were believed to be preparing to release the vessel last night after being paid up to $3.5 million (£2.3 million), the biggest ransom on record. The MV Faina was hijacked more than four months ago.

US warships and helicopters have kept a watch amid fears that her 33 T72 tanks and other weaponry could fall into the hands of Islamists who are waging a bloody insurgency on land.

Last night Andrew Mwangura, of the East African Seafarers Association, said that talks to free the Ukrainian-operated vessel and her 20-strong crew had concluded. “We hear they are counting the money but I don’t want to say any more until the crew is on dry land,” he added. “The ship could be released in the middle of the night or at daybreak.”

A businessman in the town of Galkayo said: “The crew will be free anytime from now.”

Up to 50 pirates may have been involved. The ship’s Russian captain died soon after the hijacking from a stroke, according to the first mate.

Small dinghies brought food and water from the mainland to the 150m long vessel to feed the crew of Ukrainians, Russians and a Latvian. The pirates made sure they could celebrate the end of Ramadan by bringing aboard a consignment of goats to barbecue on deck.

The record Faina ransom follows a lucrative few months for Somalia’s modern-day brigands. They snatched 42 ships in the Gulf of Aden and the Indian Ocean in 2008 in a series of increasingly bold attacks. Their success provoked an unprecedented international response. Europe, Nato, Russia, India and China all sent warships to police shipping lanes.

Insurance companies raised their premiums for cargo routed through the troubled waters and private military contractors began hiring out security teams to protect shipping. Last month pirates released the Sirius Star, laden with $100 million of oil, after being paid $3 million. The cash arrived by parachute. Five pirates later drowned as they made their escape.

A Somali negotiator in the port of Haradheere claimed that the money had been delivered. The business was worth up to $30 million last year, according to the Royal Institute of International Affairs.

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