* Three convicted murderers executed by Hamas security forces
* Executions not authorised by Palestinian President Abbas
* Human rights groups condemn the sentences

Security forces from the Islamist group Hamas executed three convicted Palestinians at dawn on Tuesday, a move condemned by local and international human rights groups and likely to lead to deeper division among Palestinian factions.
The three were found guilty of murder in separate cases and sentenced to death after a trial and all appeals were exhausted, Hamas said. Two were executed by firing squad and the third, a policeman, was hanged, security sources said.
"To achieve public deterrence and block crime, the relevant authorities implemented at dawn on Tuesday execution rulings against three convicted of horrifying murders," the general prosecutor's office in Gaza said in a statement.
Hamas, which has been in control of Gaza since 2007, had been under pressure not to carry out the executions, with the European Union and United Nations joining in calls from human rights groups for the decision to be set aside.
Under Palestinian law, Palestinian President Mahmoud Abbas has to agree to the use of the death penalty. Because of splits between Hamas and Abbas's Fatah party, the Islamists did not receive approval from the president for the sentence.
The policeman put to death was employed by the Palestinian Authority, the Fatah-led administration based in the West Bank, which has ever diminishing influence in Gaza.
In a statement, the Palestinian Authority said the executions were illegal.
"Carrying out the executions represents a flagrant violation of the Palestinian basic law," Ahmed Brak, the attorney general based in Ramallah, told Reuters.
He said those who participated in the executions were complicit in murder and would be subject to law at the "local and international level".
Human rights groups last week demanded that Hamas hold off on the executions, but the Gaza-based attorney general said the sentences could be carried out.
The Palestinian Centre for Human Rights said enforcing the death sentence without the Palestinian president's ratification constituted extra-judicial execution. International human rights groups condemned the decision.
"The death penalty is an inherently cruel and irreversible punishment in all circumstances," said Sari Bashi, the director for Israel and Palestine at Human Rights Watch.
"It's particularly egregious to execute defendants sentenced in Gaza, whose court system is rife with coercion, torture and compromised procedures," she added.
In recent weeks there have been several murders in Gaza, leading to pressure on Hamas to crack down on perpetrators.