Hamas today continued with its summary executions of "collaborators" and publicly killed four more Palestinians suspected of spying for Israel, following the targeted assassination of three of its top commanders earlier in the week.

Masked Hamas militants fatally shot the Palestinians in the courtyard of a mosque in the Jabaliya refugee camp on charges of spying for the enemy, in what was seen as a warning to the people of Gaza.

Hamas-affiliated Al-Majd website quoted security sources as saying that the four were executed in a "revolutionary" way after "legal measures were completed".

The website has warned that future collaborators would be dealt with in the field to create deterrence.

The Islamist faction declined to release the names or pictures of the executed for the sake of social stability, fearing backlash against their families.

Today's executions raise the total number of Palestinian "suspects" paraded to their deaths to 25; 18 of them were executed yesterday and three the day before.

Hamas, the militant group that rules Gaza, has warned that Israel will "pay the price" for killing three high-ranking leaders of its military wing, the Qassam Brigades.

Earlier, the Palestinian Authority (PA), which controls the West Bank, denounced yesterday's executions of alleged collaborators by Hamas, calling them "extrajudicial".

The PA President's office condemned Hamas for failing to abide by existing legal procedures for dealing with the cases.

Although collaboration with Israel is punishable by death in the Palestinian legal code, President Mahmoud Abbas has maintained a moratorium on the death penalty since 2005.

Amnesty International called on Hamas to halt the campaign of summary executions of suspected collaborators.

"This flurry of executions by Hamas is made even more shocking by the fact that the victims were sentenced to death after trials which, if they happened at all, were summary and grossly unfair," said Anne FitzGerald, Amnesty International's Director of Research and Crisis Response.

"Hamas must immediately and totally cease its use of the death penalty," Fitzgerald added.

"To put people to death following summary and grossly unfair proceedings is clearly cruel and inhumane. Hamas must also remember that the right to a fair trial before a competent court remains in force during times of armed conflict," he stressed.