The Islamist Hamas group in Gaza said Saturday "radical measures" would be taken against Palestinians who "collaborated" with Israel, a week after one of its military commanders was murdered.
Interior ministry spokesman Iyad al-Bozum said measures to be taken soon could mean arrests, trials and even executions.
During the summer 2014 conflict between Israel and Hamas in the Gaza Strip, the group's armed wing publicly executed six men accused of collaboration.
On March 24, gunmen in the Palestinian territory shot dead Hamas official Mazen Faqha, who had been freed by Israel in a 2011 prisoner swap, in what appeared to be a planned assassination.
Faqha was released along with more than 1,000 other Palestinians in exchange for Gilad Shalit, an Israeli soldier Hamas had detained for five years.
After Faqha was killed, Hamas pointed the finger of blame at "collaborators" and at Israel.
Earlier Saturday, Hamas said it would allow foreign UN and Red Cross workers to leave the enclave after it closed the only foot crossing with Israel.
It shut the Erez crossing a day after it blamed the Jewish state for Faqha's death.
"In recognition of the need for humanitarian aid in Gaza, the Ministry of Interior decided to permit foreign workers of the UN and the Red Cross free movement to enter and leave the Gaza Strip," a ministry spokesman said.
Other restrictions remain in place, a statement added, but "humanitarian cases in urgent need of travel" would be examined individually.
On Monday, the authorities reopened Erez for those entering Gaza, but men between 18 and 45 are still largely prevented from leaving the enclave of two million people.
Reports said Hamas was looking for the assassins of Faqha, 38, believing they are still in the territory, but the knock-on effects have been significant.
On Friday, the office of the UN Special Coordinator for the Middle East Peace Process suspended its missions to Gaza as frustrations grew over the restrictions, according to a source close to the organisation.
Around half a dozen international aid workers were prevented from leaving this week, a senior humanitarian source has said.
The World Health Organization said that, until Friday, 79 Gazan patients had missed medical appointments in Israel because of the restrictions.
More than two-thirds of Gazans are dependent on aid, the United Nations says.
Erez is the only crossing for people, although a separate route is available for goods.
On Thursday, a coalition of more than 100 Palestinian NGOs and rights groups called on Hamas to reopen the crossing.
Israel has maintained a blockade on Gaza for a decade, largely restricting residents from entering.
However, Israel grants hundreds of permits for medical, educational, business and other reasons per week.
Hamas has fought three wars with Israel since 2008.
Gaza City, Palestinian Territories | AFP
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