For the second day in a row, Hamas and Islamic Jihad cells fired rockets and mortar shells at Jewish settlements.
No casualties were reported on Wednesday, after three workers were killed by a mortar shell the day before.
An Israeli aircraft on Wednesday afternoon fired three missiles at Palestinian resistance fighters near the town of Khan Yunis in the Gaza Strip, without causing casualties.
The Israeli occupation army said it targeted a mortar launcher that had just been fired and another that was about to be used, as well as a car loaded with mortars.
Witnesses said three fighters from the Islamic group Hamas fled as the missiles struck. No one was hurt.
An army spokeswoman said the aim of the strike was only to destroy the weapons.
Abbas is expected to remain in Gaza for several days, holding talks with Hamas and Islamic Jihad leaders as well as his Fatah party about a range of issues and disputes.
The upsurge in violence, endangering a truce declared four months ago, was Abbas's first subject. On arrival in Gaza, he denounced the Israeli air strike.
"It's an unjustified operation, because it will destroy the truce," he said.
"It's an unjustified operation, because it will destroy the truce"
Israel's Army Radio reported that Israeli Defence Minister Shaul Mofaz was to meet his Palestinian counterpart, Interior Minister Nassr Yousef, later on Wednesday. The report said Mofaz would demand action to end to the rocket attacks and would discuss the pullout.
Sharon led a ministerial meeting on Wednesday where preparations for the withdrawal were discussed.
The meeting was uncharacteristically opened to journalists, in an apparent effort to dispel impressions that the government isn't ready to provide alternative housing, jobs and schools for the 9000 settlers who are to be relocated.
"The evacuation will take place on schedule," Sharon said, criticising "incitement", threats and pressure on the settlers by opponents of the pullout.
Sharon faces fierce resistance to
his Gaza disengagement plan
Officials said only about half of the settlers slated for evacuation are in talks with the government about moving, defying calls by their leaders to oppose the plan at all costs, officials said.
Pullout opponents have urged settlers not to cooperate with the pullout plan, and some settlers who have said they are ready to go, say they have been threatened and ostracised.
"They are not concerned with the fate of the settlers and their children," Sharon said. "They are willing to create great suffering on top of the suffering the evacuation will inflict, in order to achieve their political aims."
In other news, Palestinian President Mahmoud Abbas has urged Israel to sanction the reopening of the Gaza Strip airport and back "safe passage" between Gaza and the West Bank.
Abbas made the appeal on Wednesday in talks with James Wolfensohn, the Middle East quartet's special envoy for Israel's disengagement project.
Abbas said Israel should let the airport and the route for safe passage reopen after withdrawing from the occupied Gaza Strip this summer, Palestinian Civil Affairs Minister Mohammed Dahlan, who was present as the meeting, said in the West Bank city of Ram Allah.
The international airport in southern Gaza, near the town of Rafah on the Egyptian border, was opened in 1998 and closed by Israel in 2001 following the outbreak of the Palestinian uprising.
Mohammed Dahlan says Israel
should reopen Gaza airport
The "safe passage" linking Gaza to the occupied West Bank was also opened under great pomp and ceremony in October 1999, only to be closed within months, similarly for security reasons.
It had allowed Palestinian people and goods free movement between the two territories.
In another development, Israeli forces on Wednesday imposed a curfew on the village of Marada, south of the West Bank city of Nablus.
Residents said Israeli forces wanted to prevent them from staging demonstrations against the building of the separation barrier on the village's lands.
Witnesses said three foreign supporters were arrested and prevented from reaching the village.