Israel prevented thousands of Palestinians from returning to northern Gaza on Sunday, accusing Hamas of violating a fragile cease-fire by altering the order of released hostages, while local officials reported Israeli forces killed two and wounded nine by firing on the crowds.

Under the Israel-Hamas ceasefire, Israel on Saturday was to begin allowing Palestinians to return to their homes in northern Gaza on foot through the so-called Netzarim corridor bisecting Gaza. Israel put the move on hold until Hamas frees a hostage who Israel said was supposed to have been released Saturday. Hamas in turn accused Israel of violating the agreement.

Crowds of people traveling by foot and carrying their belongings crowded a main road leading to a closed Israeli checkpoint. "We have been in agony for a year and a half,” Nadia Qasem, a woman displaced from the north said as she waited. "Since 1 a.m. we have been waiting to return.”

Fadi al-Sinwar, who was also displaced from Gaza City, said, "the fate of more than a million people is linked to one person,” referring to the Israeli hostage.

"See how valuable we are? We are worthless," he said.

Israeli forces fired on the crowds on three occasions overnight and into Sunday, killing two people and wounding nine, including a child, according to al-Awda Hospital, which received the casualties.

There was no immediate comment from the Israeli military.

Israel has pulled back from several areas of Gaza as part of the ceasefire, which came into force last Sunday, but the military has warned people to stay away from its forces, which are still operating in a buffer zone inside Gaza along the border and in the Netzarim corridor.

Hamas freed four young female Israeli soldiers on Saturday, and Israel released some 200 Palestinian prisoners.

But Israel said another hostage, the female civilian Arbel Yehoud, was supposed to have been released ahead of the soldiers and that it would not open the Netzarim corridor until she was freed. It also accused Hamas of failing to provide details on the conditions of hostages set to be freed in the coming weeks.

Hamas accused Israel of using the issue as a pretext to delay the return of Palestinians to their homes. In a statement, the resistance group said it had informed mediators that Yehoud was alive and provided guarantees that she would be released.

The United States, Egypt and Qatar, which mediated the cease-fire, were working to address the dispute.