The coastguards persuaded Inmarsat, which runs international satellite communications, to open a free link with the vessel. And they discovered the sailors had been stuck there for six months with no supplies and no money to enable their return to the Ukraine.
One of the men explained they had been abandoned by the ship's master after the ship was arrested over $1m debts allegedly owed to a Greek bank. Although they were not under arrest, they feared they would lose any chance of wages that were owed them if they left the boat.
Henry Purbrick, from the Falmouth coastguard, said they alerted the owner's lawyer in Greece. But on Thursday they received further cries for help and called for international action to help the men.
"They sounded even more desperate. Can you imagine being in Egypt and no way of getting home?" Mr Purbrick said.
Mykola Kravchenko, of the Ukrainian embassy in London, said he was saddened by the case but it was not rare. "They have to fend for themselves," he said. "We are a country in crisis."