"Let's leave the killing, aggression and destruction to Israel, because that's enough for the Palestinian people," said Mohamed Subaih, the Arab League's assistant secretary-general for Palestinian affairs.
"This infighting is unprecedented Palestinian madness," Subaih added.
Fatah gunmen on Tuesday threatened to kill leaders of the governing Hamas militant group, escalating a power struggle marked by the worst internal violence in Gaza and the West Bank since the Palestinian Authority's creation in 1994.
Twelve Palestinians have been killed and more than 100 wounded in two days of fighting between militants from President Mahmoud Abbas' Fatah party and Hamas. Abbas has been locked in a power struggle with Prime Minister Ismail Haniyeh of Hamas over stalled efforts to form a unity government.
'PM, President responsible'
Subaih said that the infighting was the greatest threat to the Palestinian cause and made it hard for the Arab League to argue on the Palestinians' behalf. The League needed a unified Palestinian stance, he said.
"This was a clear request from the Arab League and the foreign ministers, that the Palestinian stance be unified so we can address the world," Subaih said.
He said that the 22-member League was in frequent contact with the various Palestinian groups to put an end to the fighting, which he said served Israel's interests.
Subaih said responsibility for the fighting lay with every citizen and official, including the president, the prime minister and the cabinet.