By Nidal al-Mughrabi
GAZA, May 18 (Reuters) - Israel struck at Hamas targets in Gaza on Friday, killing at least one man, and threatened further action to stop rocket attacks, while Palestinian rival factions fought each other in turmoil that verged on civil war.
Palestinian President Mahmoud Abbas, whose Fatah faction has been accused by Hamas of joining forces with Israel against it, called U.S. Secretary of State Condoleezza Rice to ask her to halt an Israeli "military escalation", a Palestinian news agency said.
Fatah and Hamas forces, locked in a week-old round of fighting, waged a fierce battle in Gaza City in which witnesses said three rocket-propelled grenades were fired at the pro-Hamas Islamic University campus.
Prime Minister Ismail Haniyeh, a Hamas leader, called on Palestinians to unite against "Israeli aggression" and cease internal fighting.
"All members of the security services should abide by the instructions of the political leadership and return to their positions and bases, and also all gunmen should pull out of the streets," Haniyeh told reporters.
Truces agreed by Islamist Hamas and secular Fatah over the past week have collapsed swiftly. Nearly 50 people have died in the deadliest internal violence since the two rival groups formed a unity government in March.
In Tel Aviv, Israeli Foreign Minister Tzipi Livni told foreign ambassadors the government may decide further action within days and noted the cabinet would meet as usual on Sunday.
"We will see sustained and vibrant measures to end the rocket attacks and remove the threat to southern Israel," government spokesman David Baker said.
Israeli forces have recently completed training for a possible ground offensive in the Gaza Strip, from which they and Israeli settlers withdrew in 2005.
GUNSHIPS
A Palestinian hospital official said at least one man was killed and others were wounded when Israeli helicopter gunships fired on them after they launched a rocket into Israel.
The Israeli military said it attacked a rocket crew in the northern Gaza Strip and that eight improvised Qassam missiles had struck Israel on Friday morning alone. One hit a house in the town of Sderot. Medics said there were only minor injuries.
Tanks and some other troops took up positions on Thursday, just inside the crowded coastal enclave in a move the military called "defensive".
At least nine Hamas fighters have been killed in Israeli strikes since early Thursday. Militants from Gaza have fired about 100 rockets at the town of Sderot and its surroundings in the past week, causing several injuries but no deaths.
"For too long the international community took this situation in the southern part of Israel as acceptable, as part of life in Israel, and it's not. Enough is enough," Livni said, citing a need to put pressure "on these terrorists".
Abbas was quoted by Wafa news agency as asking Rice "to stop the Israeli military escalation against our people and continue their efforts to push the peace process forward".
The Palestinian Authority has been crippled since Hamas, which refuses to recognise Israel, won parliamentary elections early last year, prompting Israeli and international sanctions.
(Additional reporting by Avida Landau and Alastair Macdonald in Jerusalem)