GAZA CITY (AFP) - Israeli tanks massed at the Gaza border on Sunday as warplanes again pounded the impoverished enclave of 1.5 million people where raids have killed nearly 290 people in less than two days.

Dozens of tanks and personnel carriers idled at several points near the border after Israel warned it could launch a ground offensive in addition to its massive air blitz, AFP photographers reported.
Hamas responded to the ongoing bombardment by firing rockets the farthest yet into Israel, with one striking not far from Ashdod, Israel's second-largest port, some 30 kilometers (18 miles) north of Gaza. It caused no casualties, medics said.
The Islamist movement accused Israel of ""committing a holocaust as the whole world watches and doesn't lift a finger to stop.""
""The Palestinian resistance reserves the right to hit back at this aggression with martyr operations,"" spokesman Fawzi Barhum told reporters, referring to suicide bombings which Hamas hasn't carried out against Israel since January 2005.
Britain and Russia joined the growing international chorus for a halt to the violence.
Pope Benedict XVI implored the international community to do ""all it can to help the Israelis and Palestinians on this dead-end road... and not to give in to the perverse logic of confrontation and violence.""
But Israeli Defense Minster Ehud Barak vowed to ""expand and deepen"" the bombing blitz.
""If it's necessary to deploy ground forces to defend our citizens, we will do so,"" his spokesman quoted him as saying.
The cabinet gave the green light to call up 6,500 reserve soldiers, a senior official told reporters after the meeting.
Warplanes continued to pound the overcrowded territory, where many streets were deserted and schools and shops stayed shut as hundreds of funerals were held.
Jets bombed a series of tunnels on Gaza's border with Egypt – a lifeline for Hamas used for smuggling in goods into the enclave, which has been virtually sealed by Israel since the Islamists seized power in June 2007.
At least two people were killed in the bombing.
Dozens of Gazans tried to break through the border into Egypt following the strikes, but were stopped by Egyptian police firing into the air, said an Egyptian security official.
Businesses in the occupied West Bank, including annexed Arab east Jerusalem, observed a strike in protest at the onslaught that one Palestinian human rights group called ""the bloodiest day in the history of the (Israeli) occupation.""
Since early Saturday, at least 287 people have been killed and more than 600 wounded, medics said.
The Israeli bombardment has sparked widespread international concern.
In New York, the UN Security Council called for an ""immediate halt to all violence"" and urged all sides ""to stop immediately all military activities.""
In Rome, the pope said that ""the terrestrial homeland of Jesus cannot continue to be the witness of such bloodshed which is repeated ad infinitum.""
Egypt, which had brokered a six-month truce between Israel and Hamas that expired on December 19, said it was trying to negotiate a new ceasefire.
But a senior Israeli official told AFP that ""we have our goals and our timetable and we don't seek mediation.""
The Israeli offensive sparked protests in the occupied West Bank, where one demonstrator was killed in clashes with police. More than 50,000 rallied in Egypt and hundreds in Dubai.