Security forces in the Hamas-ruled Gaza Strip have started arresting suspected "collaborators" with Israel after a month-long amnesty ended, a Hamas official said on Saturday.
"Since yesterday (Friday), we arrested several collaborators with the Israeli occupation," interior ministry spokesman Islam Shahwan told AFP, declining to give a number.
On March 12, Hamas announced a month-long grace period for collaborators to turn themselves in in return for leniency.
Shahwan said that some people had surrendered during the amnesty but did not give details on their likely treatment.
Under Palestinian law, collaboration with Israel is punishable by death.
All executions must be approved by the Palestinian president before they can be carried out, but Hamas no longer recognises the legitimacy of incumbent Mahmud Abbas, whose four-year term ended in 2009.
A Gaza official said that five or six suspects fled into neighbouring Israel before they could be apprehended.
During an eight-day conflict with Israel last November, at least seven people were gunned down after being accused of being collaborators.
The bodies of six were dragged behind vehicles through the streets of Gaza City.
The killings were claimed by Hamas militants from the Ezzedine al-Qassam Brigades in notes pinned to their bodies, which accused them of being traitors.
New York-based Human Rights Watch criticised Hamas on Thursday for failing to honour promises to investigate the killings.
"Hamas's inability or unwillingness to investigate the brazen murders of seven men makes a mockery of its claims that it is upholding the rule of law in Gaza," HRW's Middle East director Sarah Leah Whitson said in a statement.
Despite sweeping Palestinian parliamentary elections in 2006, the Islamist movement remains blacklisted as a terror group by both the European Union and the United States.