Medical charity Doctors Without Borders (MSF) said Saturday it is "concerned" over claims by migrants reaching the Greek island of Kos on inflatable boats that they were attacked at sea.

Several people from Syria and Iraq who have arrived on Kos in the past week told AFP they had been attacked by masked gunmen at sea, with some claiming the assailants stole their fuel and even motors.

Some accused the Greek coast guard of assaulting them.

"We have heard enough stories for us to be concerned," MSF humanitarian affairs officer Constance Theisen told AFP.

Greece's coastguard said on August 1 that it had arrested three men on the island of Samos, some 100 kilometres north of Kos, suspected of preying on migrants seeking to cross over from Turkey.

They were dressed like Greek coastguards and wore hoods, the coastguard said.

An international humanitarian group in late July said it had begun investigating claims that "mafia gangs" or "special commandos of the Greek coastguard" were involved in such attacks, notably in the area of the island of Lesbos.
The head of the Greek police's immigration department, Major General Zakharoula Tsirigoti, has denied the claims outright.

MSF, which has been working in the Aegean islands since March, first heard such claims from migrants in July, Theisen said.

In Kos, Ahmad Yousef, a 40-year-old refugee from Baghdad, said his boat had been attacked on a previous failed attempt to reach Greece.

"Big, tall men with their faces covered, carrying weapons, sticks and knives approached our boat, punctured it, and threw our motor into the water," Yousef said.

Walaa, who is also Iraqi, claimed he tried to reach Kos, just a few miles from the Turkish mainland near southwestern Bodrum, on a wooden yacht on August 6, but that it was attacked by a Greek boat.

"(It) drove straight into ours, breaking our yacht in two. The fuel tank exploded and a fire broke out. We were all thrown into the water. There were women and children among us," said Walaa, 40.

"Then when the Greeks saw what happened, they decided to pull us out of the water and bring us to land... They apologised and said sorry, 'we just wanted to scare you away,'" he told AFP.

Ibrahim Najjar, a 21-year-old from Syria, said that on a previous attempt to reach Greece two weeks ago, his boat was approaching the island of Mytilene, near Lesbos.

"A boat with a big EU flag and a little Greek flag approached ours, and the men on board pulled out weapons," Najjar said.

"They all had their faces covered. They took the fuel from our boat and sped off," he said.

- 'Inhumane methods' -

MSF's Theisen said the charity's teams have heard similar accounts from several people, some of whom have given "signs that point towards the Greek coast guard".

A Turkish government official told AFP in Istanbul: "Unfortunately, the other (Greek) side resorts to inhumane methods including attacking boats."

He added: "They are not addressing the problem of migrants."
Meanwhile, MSF says it has heard other accounts accusing the Turkish coast guard of preventing migrants from leaving Turkey.

MSF has voiced its concern over the claims -- which it cannot confirm -- with the Greek coast guard, the interior ministry and European border patrol agency Frontex.

UN refugee agency spokeswoman Stella Nanou told AFP that UNHCR has heard such claims, but that it could neither confirm nor deny them.

"We have heard such allegations, and now we are trying to monitor the situation in order to be able to assess," Nanou said.