Palestinian Authority President Mahmoud Abbas has called for Gaza's Hamas rulers to be "brought down", his strongest call yet for their removal.

Previously he has only demanded Hamas apologise for taking over Gaza and return it to Fatah security control.

His comments came after Hamas security forces killed eight Fatah members at a rally in Gaza on Monday.

A Hamas leader in Gaza, Ismail Haniyeh, has expressed regret for the deaths, and promised a public investigation.

He also said members of Hamas' security forces might have been at fault, and said he had ordered the release of people arrested if there was no evidence against them. But he added: "The guilty will be punished under the law."