Hundreds of Palestinians stormed the Gaza Strip's border crossing with Egypt on Wednesday, throwing rocks at Egyptian troops and demanding to cross through, witnesses said.

The Palestinians accused Egypt of reneging on a promise to open the vital crossing, which has been virtually sealed for the past year since the Hamas militant group seized control of Gaza. But Egyptian officials said Hamas had broken the agreement by sending unauthorized people to cross.

The crowd burst past Hamas security forces at the border but was unable to get through the Egyptian side, the witnesses said. Palestinians began throwing rocks at Egyptian troops, who responded with water cannons. No one made it across the border, and Hamas later restored order, the witnesses said.

Rafah is the main gateway for Gazans to the outside world, used by the area's 1.4 million people to travel abroad for studies, medical care, jobs and family visits.

In January, Hamas militants blew open the border, allowing thousands of people to cross through until it was resealed about two weeks later. Wednesday's rush on the border raised concerns that people might once again try to breach the border.

Egypt and Israel have kept Rafah closed for the past year to put pressure on Gaza's Hamas rulers. Under a truce mediated by Egypt, Israel has signaled it would reopen the border once Hamas returns a captive Israeli soldier it has held for two years. Egypt is currently trying to broker a prisoner swap.

As part of the truce, Egypt had allowed in principle to allow medical patients, students and those with residence in Arab countries to leave over three days, starting Tuesday. At least 6,000 Gazans meeting these criteria registered to cross Rafah.

However, on Tuesday, only about 150 people were allowed out by Egyptian border officials who moved very, very slowly, according to Ehab Ghussen from the Gaza Interior Ministry.

On Wednesday, thousands were still waiting at the crossing, and by noon, not a single bus had crossed yet. Tensions rose after Egypt said only 200 people would be allowed through, and the crowd started pushing through the first gate on the Gaza side, up to the last gate that separates Gaza and Egypt.

Hamas spokesman Sami Abu Zuhri said his group was "sorry" for the troubles at the border.

"This reflects the pressure that are people are suffering," he said. "We call on Egypt to speed up the process of reopening Rafah terminal in normal way."

In Egypt, security officials and a Palestinian diplomat said the decision to open the crossing this week was made under an agreement that both Hamas and Egypt should coordinate the movement.

An Egyptian official, speaking on condition of anonymity because he was not authorized to talk to the media, said Hamas had violated the agreement by sending people who were not approved to cross.

"This an infringement of the agreement of coordination," the official said. "The opening of the crossing was for humanitarian purposes not for every body," he said.