The fires, which began on Tuesday, have erupted throughout the country, blazing through parched forests, incinerating scores of homes and forcing tens of thousands of people to flee. Two prisons were also evacuated.
Prime Minister Benjamin Netanyahu said on Friday that “a considerable number” of the fires were set and described them as “terror,” a term usually given to militant attacks by Palestinians.
“There is a price to crime, and there is a price for terror and incitement, and we will exact it,” Mr. Netanyahu said while on a tour of the Hatzor military base, according to local news reports. “The instructions are to prosecute anyone committing these acts so that all can see that anyone who tries to burn down the state of Israel will face the fullest punishment.”
Firefighters had most of the dozens of fires under control by Friday, allowing thousands of people to return to their homes in the northern port city of Haifa, one of the areas that was hit hardest. Still, new fires erupted near Jerusalem and in the Galilee in northern Israel. Hundreds of residents of Nataf, a small Jewish community near Jerusalem, were evacuated from their homes Friday evening, fleeing another fire.
By Friday evening, a 747 Supertanker firefighting plane from the United States had landed in Israel to be used to extinguish some of the blazes and 50 American firefighters were expected to join the effort, Israeli news media reported.
While unusually hot, dry conditions and strong winds helped fan the flames, almost half of the fires are suspected of being arson, according to assessments by Israeli security officials.
The “consensus is that this is arson,” Israel’s public security minister, Gilad Erdan, told journalists on Friday. In one instance, Mr. Erdan said, his forces had found evidence that gasoline was used to start a fire in Zikhron Yaaqov, a town in northern Israel. A man from a Jerusalem was arrested with fire-making materials, he said.
By Friday evening, another two fires had been set on the Lebanese side of the border, apparently in hopes that the wind would carry the flames into Israel.
Of the 22 people arrested on arson charges, one was a Palestinian who was arrested on suspicion of causing a fire that broke out early Friday in forests around the tiny Jewish community of Beit Meir near Jerusalem, the Israeli news media reported. Eight were released, and 14 had their remand extended.
There was no further information available about the people being questioned.
Israeli officials hinted that they suspected Palestinians were behind the arsons, but Arab leaders in Israel urged caution against blaming their community without proof.
“Whoever burns down the country cannot be a citizen of the country and their citizenship status should be revoked,” said Miri Regev, the culture minister, a threat usually reserved for Palestinian citizens of Israel, who form about one-fifth of the country’s population of eight million.
If Palestinians set some of the fires, it would be a new and potentially disruptive tactic in a long-simmering conflict.
Israeli officials were “accusing the Arab minority of arson, before any formal police investigation took place,” Jamal Zahalka, a legislator in the Joint List, the Palestinian bloc in the Israeli Parliament, said in a statement.
“It is unfortunate when elected officials choose to enhance the division in the Israeli society and add fuel to the fire,” he said.
Some analysts also urged calm. The wave of fires was unusual, but it should not be overblown at this point, Alex Fishman, a military affairs analyst at the Israeli newspaper Yediot Aharonot, wrote in his column.
“If the investigations do not clearly show that this was coordinated by terror cells who were handled by one source to set fires simultaneously, then any attempt to depict these events as a fire Intifada is another effort by politicians to intimidate and distract,” he wrote.
In the past, Jewish extremists have used fires in the West Bank to torment Palestinians, setting olive fields and vehicles ablaze. In the worst such episode, in July 2015, a baby was killed and his parents later died of their injuries after arsonists set their home ablaze in Duma, a West Bank village.
After the fires this week, Israelis described harrowing moments as they fled their homes.
Yaakov Lehman, who lives in Beit Meir, said he was awakened early Friday by neighbors knocking frantically on his door, yelling that the family had to evacuate.
Mr. Lehman, 31, a native of Tucson, said he and his wife, Rachelli, who is four months pregnant, grabbed their two small children, ages 1 and 3, passports and water, and tried to find a way out of the tiny community. But the main road was ablaze and the fire was creeping in, Mr. Lehman said. Eventually, firefighters cleared a back road for hundreds of the community’s residents to flee. Mr. Lehman recorded a video of their escape on his phone from his vehicle.
Dozens of fires also broke out in the neighboring occupied West Bank, Nael al-Azzeh of the Palestinian Civil Defense forces, told local news outlets. He said they were still investigating the causes of those fires. One of them was near Yizhar, a Jewish settlement in the northern West Bank, Israeli news media reported.
Some Palestinians and Arabs took to social media to celebrate the fires, but Palestinian officials and some religious clerics reprimanded them sharply and urged people not to rejoice in the misfortunes of others.
The Palestinian Authority sent eight firefighting teams to assist, including four to Beit Meir, the Israeli news media reported.
The fires are the worst in Israel since 2010, when a blaze burned for four days and killed more than 40 people, most of them cadets from the prison service on their way to evacuate a prison.