GAZA CITY, 3 December 2005 — Israel has accused Palestinians of allowing 15 Hamas fighters back into the Gaza Strip from Egypt through the Rafah border crossing and threatened to impose economic sanctions on the strip. The dispute threatens to undermine the biggest diplomatic breakthrough since Israel’s withdrawal from Gaza.

Palestinian security officials acknowledged that wanted men have entered Gaza, but said anyone with a Palestinian identity card can come into the coastal strip. They said Israel was making demands that are not part of the crossing accord.

Israel closed the Rafah crossing — Gaza’s main gateway to the outside world — shortly before withdrawing from the strip in early September. The crossing reopened last week after months of wrangling between Israel and the Palestinians over security procedures.

Israel feared fighters or arms would flow into Gaza through Rafah, but agreed to let the border reopen after the Palestinians accepted the presence of European monitors and installed security cameras that were to let Israel monitor the crossing live.

Yesterday, Israeli officials said the Palestinians were allowing fighters into Gaza and that they were helpless to prevent the wanted men from entering.

Raanan Gissin, a spokesman for Prime Minister Ariel Sharon, said “between 10 and 15” wanted men had entered Gaza from neighboring Egypt in recent days.

“We know this, but we have no ability to stop them because we are relying on the people there — the Europeans and Egyptians,” he said, adding that Israel is talking to the other sides to improve the situation.

Israel also complained that the information it was receiving had been delayed. “Israel will not allow there to be a violation of the agreements as they were reached with Condoleezza Rice,” Gissin said, referring to the US secretary of state who clinched the border deal.

On Thursday, Sharon threatened to severe a customs union with the Palestinian areas if the Rafah operation did not improve — a step that could harm Gaza’s already weak economy. Rashid Abu Shbak, the security chief in Gaza, said Israel’s complaints were unfounded. He said under the Rafah deal, anyone with a Palestinian identity cards is allowed through the crossing.

A security officer in Gaza confirmed at least 10 fugitives who fled Gaza before and during the first Palestinian uprising in the late 1980s had returned. The officer said most of the men were members of Hamas. Their ranks included Ahmed El-Malah, one of the group’s founders, and Fadel Zahar, brother of Hamas leader Mahmoud Zahar. Both men were deported from Gaza by Israel years ago. Fadel Zahar said he was exercising his right to return. “I am a resident of Gaza. My family lives here. I spent all my life here but I was deported for political reasons in 1991,” he said in an interview.

He said he has spent his time in exile in Lebanon, Sudan and most recently, Syria. But he denied reports that he is a Hamas leader.

“I am a member of Hamas, I am not a leader of Hamas, I am proud of this membership,” he said.

— Additional input from agencies