Israel has refused entry to a Greek-flagged vessel carrying peace activists to the Gaza Strip, on the 20th day of attacks on the costal sliver.

Israeli warships threatened to open fire at the Arion on Thursday, after they intercepted the boat in the international waters.

The boat which was carrying peace activists from the US "Free Gaza" group, doctors, aid workers, European parliamentarians and medical aid for casualties of Gaza carnage was then forced to return to Cyprus.

"The boat has turned around and is coming back -- it has been underway for several hours," said Karin Pally, a coordinator for the US-based Free Gaza Movement.

"Apparently the gunboats threatened to shoot at them or stop them by any means, so a decision was taken to return to Larnaca," she added.

An earlier attempt by the Free Gaza Movement to break Israel's blockade on Gaza ended on December 30, when an Israeli navy vessel collided with the vessel. Passengers said it was a deliberate ramming.

The Free Gaza group has made five deliveries of aid to Gaza since August, defying a blockade imposed by Israel since the democratically-elected Hamas took the control of the enclave in 2007.

Israel's disproportionate assault on Gaza continues in full strength on the 20th day of the carnage, killing seven more people in the northern town of Jebaliya.

The onslaught has so far claimed the lives of 1,066 Palestinians while leaving some 4,700 other wounded.

AO/MMN