No injuries were reported in the attacks, which left church doors charred and walls pockmarked with bullet holes and scorched by firebombs. Churches of various denominations were targeted.
Relations between Palestinian Muslims and Christians are generally peaceful, and the attacks on the churches sparked concern that tensions would heighten.
"The atmosphere is charged already, and the wise should not accept such acts," Father Yousef Saada, a Greek Catholic priest in Nablus, said Saturday.
Ayman Daraghmeh, a legislator from the ruling Islamic militant Hamas group, denounced the attacks. Dozens of police took up position around churches in Nablus to protect the holy sites.
Firebombings left black scorch marks on the walls and windows of Nablus' Anglican and Greek Orthodox churches. At least five firebombs hit the Anglican church and its door was later set ablaze. Smoke billowed from the church as firefighters put out the flames
In a phone call to The Associated Press, a group calling itself the "Lions of Monotheism" claimed responsibility for those attacks, saying they were carried out to protest the pope's remarks in a speech this week in Germany linking Islam and violence.
Later Saturday, four masked gunmen doused the main doors of Nablus' Roman and Greek Catholic churches with lighter fluid, then set them afire. They also opened fire on the buildings, striking both with bullets.
In Gaza City, militants opened fire from a car at a Greek Orthodox church, striking the facade. A policeman at the scene said he saw a Mitsubishi escape with armed men inside. Explosive devices were set off at the same Gaza church on Friday, causing minor damage.
Greek Orthodox church in Nablus (Photo: AP)
There were no claims of responsibility for the last three attacks Saturday.
"The people who did this are uneducated and ignorant," said the Gaza church's prelate, The Rev. Artinious Alexious.
'We are one people'
In his speech, Benedict cited an obscure Medieval text that characterizes some of the teachings of Islam's founder as "evil and inhuman." The pope, spiritual leader of more than 1 billion Roman Catholics, did not explicitly agree with or repudiate the text.
The Vatican later said the pope did not intend the comments to be offensive. However, they have sparked worldwide protests by Muslims, and Muslim leaders have demanded an apology.
George Awad, a cleric at the Greek Orthodox church in Nablus, said he and other Christians have apologized for the pope's remarks and urged Muslims to use restraint.
"There is no reason to burn our churches," he said.
On Friday, about 2,000 Palestinians protested against the pope in Gaza City, accusing him of leading a new Crusade against the Muslim world. Palestinian Prime Minister Ismail Haniyeh of Hamas said the pope offended Muslims everywhere.
Christians make up a small — and dwindling — minority of several tens of thousands among the more than 3 million Palestinians in the West Bank, Gaza and east Jerusalem. The Palestinian Authority has made considerable efforts to ensure the political representation of Christians.
Bishop Riah Abo El-Assal, the top Anglican clergyman in the Holy Land, said Saturday he expected his Muslim colleagues would swiftly denounce the attacks on the churches. He called them "childish acts" and said he was not increasing security at the Anglican churches in the area.
In Nablus, merchant Khaled Ramadan, who was dressed in traditional Islamic garb, said the pope's comments were unforgivable, but that Palestinians must not fight among themselves.
"We are one people and violent reactions like these should not happen here," he said.