Palestinian leader Mahmoud Abbas has pleaded with militant groups to stop attacks against Israel and throw their weight behind a faltering ceasefire.
Israeli war planes have hit Gaza on two consecutive days
Mr Abbas spoke as Gaza militants fired rockets at Israeli towns for a third day, at the end of a violent week.
Last night Israeli troops raided at least three West Bank towns, seizing 26 suspected militants.
US Secretary of State Condoleezza Rice will visit the region next week to urge an end to the new upsurge in violence.
Ms Rice added the stop onto a planned trip to Africa after the breakdown of the ceasefire, agreed in February.
Mr Abbas blamed Israel for effectively undermining the ceasefire, but warned Palestinian groups that he would not tolerate renewed infighting or new attacks against Israel.
Israeli Prime Minister Ariel Sharon has promised a "strong and harsh" response to the return of attacks on Israelis.
The fresh violence began with a series of Palestinian rocket attacks on an Israeli town, in which one woman died, and a suicide bombing that killed six Israelis - the first in four months.
Truce in tatters
Overnight Israeli troops rounded up suspected members of the Palestinian militant movements Hamas and Islamic Jihad in Hebron, Nablus and Bethlehem.
Later on Saturday, Israeli aircraft hit targets in Gaza, wounding two people.
The US does not want the Gaza withdrawal put off
One Israeli missile hit a workshop in the east of the city and another was aimed at a storeroom near the sea.
Israeli air strikes on Friday killed five Palestinians, four of them Hamas militants.
The escalating tension has left the ceasefire, declared several months ago, in tatters, the BBC's Alan Johnston in Gaza City says.
In what observers say was an effort to rein in the militants, Palestinian Authority police fought a gun battle with Hamas members on the streets of Gaza City on Friday, which left two teenage bystanders dead and 25 others wounded.
During the fighting, amongst the worst between Palestinians in recent years, Hamas militants set fire to a police station, a police armoured personnel carrier and three jeeps and attacked security forces with rocket-propelled grenades.
US pullout fears
Ms Rice's trip next week will be her third to Israel and the Palestinian territories in the space of five months.
It is a sign of increasing concern in the US that Israel's planned withdrawal from Gaza next month could be disrupted because of the violence, the BBC's state department correspondent Jonathan Beale says.
"All parties need to make a maximum effort to see that this disengagement process is a success," state department spokesman Sean McCormack said.
Israel has occupied Gaza and the West Bank since 1967.
Approximately 8,500 settlers and the soldiers that protect them are due to be withdrawn from Gaza. Israel will maintain control over Gaza's borders, coastline and airspace.
About 630 settlers will also be removed from four small West Bank settlements.