Palestinian Prime Minister Ismail Haniya has denounced Israel's offensive in Gaza as an attempt to bring down the Hamas-led government.
In his first public address since Israel's campaign began, Mr Haniya said Hamas would not change its policies.
He also said the Israeli attacks were making negotiations on the release of a captured soldier more difficult.
Later Israel launched air strikes for a fourth successive night against what it says are facilities used by terrorists.
Palestinians said the latest strikes hit uninhabited areas near the Khan Younis and Rafah refugee camps in the southern Gaza Strip.
In Gaza City a car reportedly carrying militants from Islamic Jihad was destroyed. Three people were wounded, Palestinian medical sources say.
Speaking at Friday prayers in Gaza City, Mr Haniya said Israel was using Cpl Gilad Shalit's capture by militants as a pretext to bring down his government.
"This total war is proof of a premeditated plan," he told worshippers.
He said Israel's detention of dozens of Hamas officials on Thursday was "meant to hijack the [Palestinian] government's position, but we say no positions will be hijacked, no governments will fall".
Mr Haniya said he was in contact with Arab, Muslim and European leaders to try to resolve the crisis, "but this Israeli military escalation complicates the situation".
Supreme Court appeal
On Friday, Israel revoked the East Jerusalem residency rights of a Hamas cabinet minister and three Hamas MPs held in mass detentions the previous day.
BARRED HAMAS OFFICIALS
The ministry said the timing of the move was not connected to efforts to free Cpl Shalit.
A lawyer for the four men, Osama Saadi, said he would appeal to Israel's Supreme Court, the Associated Press news agency reported.
If the appeal fails, the MPs face being excluded from Jerusalem and barred from travelling freely within Israel.
About 200,000 Palestinians are residents of East Jerusalem, occupied by Israel in 1967 and later annexed in a move not recognised internationally.
Palestinian political activity in the eastern part of the city is prohibited under interim peace accords.
Talks planned
A large Israeli force remains poised on the edge of northern Gaza, held up by last-ditch attempts to negotiate an agreement.
The head of Egyptian intelligence, Omar Suliman, is due to arrive in the region on Saturday for talks with both Palestinians and Israelis.
GAZA CRISIS TIMELINE
During Thursday night's air strikes, Israeli warplanes fired missiles into the Palestinian interior ministry in Gaza City, setting the building ablaze.
At least 20 other targets included an office of Palestinian Authority President Mahmoud Abbas' Fatah group, militant training camps, a weapons storage facility in Gaza City and sites used by militants to fire rockets at Israel.
There were also reports of heavy exchanges of fire between militants and an undercover Israeli force near the northern town of Jabaliya early on Friday.
A militant was shot dead by troops in the West Bank city of Nablus, Palestinian sources said.
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