Jerusalem (CNN) Tens of thousands of residents of the Israeli port city of Haifa were allowed to return home Friday, as firefighters who have been battling wildfires for the past four days brought the flames menacing the city under control.

Authorities have warned that any fires deliberately set will be regarded as terrorism.

By Friday, 12 people had been detained in connection with the fires, police spokesman Micky Rosenfeld said, although it was not immediately clear whether they were suspected of arson or negligence.

A boy stands next to a burnt car in Zikhron Ya'akov on November 23.

A boy stands next to a burnt car in Zikhron Ya'akov on November 23.

Relly Golan surveys the ruins of her burned home in Zikhron Ya'akov on November 23.

Relly Golan surveys the ruins of her burned home in Zikhron Ya'akov on November 23.

Officials watch fires from a home that was burned in Nataf on November 23.

Officials watch fires from a home that was burned in Nataf on November 23.

A plane drops fire retardant on wildfires in the hills near Nataf, Israel, on November 23.

A plane drops fire retardant on wildfires in the hills near Nataf, Israel, on November 23.

Two people document a Haifa fire on their cell phones on November 24.

Two people document a Haifa fire on their cell phones on November 24.

A woman sprays water toward a fire from a rooftop in Haifa on November 24.

A woman sprays water toward a fire from a rooftop in Haifa on November 24.

A woman looks at a damaged building next to burned cars in Haifa on November 25.

A woman looks at a damaged building next to burned cars in Haifa on November 25.

Palestinian firefighters work in Haifa, Israel, on Friday, November 25, to extinguish the last of the wildfires that spread across Israel's third-largest city and forced tens of thousands of people to flee their homes. Israel has been battling its most serious wildfires since 2010. Days of strong, dry easterly winds have been driving the flames, Israeli meteorologist Dani Rup told CNN.

Palestinian firefighters work in Haifa, Israel, on Friday, November 25, to extinguish the last of the wildfires that spread across Israel's third-largest city and forced tens of thousands of people to flee their homes. Israel has been battling its most serious wildfires since 2010. Days of strong, dry easterly winds have been driving the flames, Israeli meteorologist Dani Rup told CNN.

The blazes scorching northern Israel began Tuesday in the northern community of Zichron Ya'akov, about 35 kilometers (22 miles) north of Haifa. Fires broke out the following day near Modi'in in central Israel.

Authorities had ordered the evacuation of 60,000 people in Haifa as fires menaced 11 neighborhoods. Strong winds Friday morning fanned new flames.

But a spokesman for Israel's Coast district police, which includes Haifa, told CNN early Friday afternoon local time that all Haifa residents were now free to return to their homes.

Mayor Yona Yahav said Thursday that 700 homes in the city had been damaged or destroyed. He described the scale of the fire as "unprecedented in Haifa."

Uri Chobotaro, of the Coast region fire and rescue services, said all the fires in Haifa are out but there is always the danger of flames reigniting from smoldering embers. The fire at Zichron Ya'akov, now extinguished, was definitely arson, according to Chobotaro.

Fires in the Nataf area of Israel have died down, effectively placing all fires in central and northern Israel under control, said Rosenfeld. Residents are not yet permitted to return and police units and firefighters remain in the area to respond as the situation requires.

A new fire broke out Friday afternoon near the Kibbutz Ma'ale Hahamisha, west of Jerusalem, Jerusalem District Fire Service spokesman Udi Gal told CNN.

Twenty planes and 30 fire trucks fought that blaze, Gal said.

Israeli police said about 100 families were being evacuated from the area, as the fire spun out of control.

Netanyahu says arsonists will be punished

Speaking to reporters Thursday, Prime Minister Benjamin Netanyahu said if the fires were deliberately set it would amount to "terrorism," and vowed to severely punish anyone who "tries to burn parts of Israel," Reuters reported.

"Every fire that was caused by arson, or incitement to arson, is terrorism by all accounts. And we will treat it as such."

An Israeli soldier helps extinguish a fire next to a house on November 25 in Haifa, Israel.

Friday morning, the Prime Minister visited the location of a large overnight fire in Bet Meir, about 25 kilometers (15.5 miles) west of Jerusalem and Tel Aviv, now brought under control.

"The most important thing is to evacuate people, and also yourselves. Nobody needs to die here, nobody," Netanyahu told firefighters.

Internal Security Minister Gilad Erdan said Thursday it was "quite clear that a good amount of the fires were caused by arson and, as the Prime Minister said, there is a new phenomenon of arson terrorism."

An Israeli firefighter plane helps extinguish a blaze in Haifa.

The fires have prompted wide discussion among Palestinians on social media. Some posts linked the fires to current proposed Israeli legislation that could ban loudspeakers broadcasting the Muslim call to prayer, suggesting the fires were a punishment from God and sparking the controversial #israelisburning hashtag on Twitter.

This celebratory response triggered an angry backlash from others, including some among Israel's Arab population, who pointed out that many who see themselves as Palestinians live in those places being ravaged by fire, or have families who originally came from these areas.

Ayman Odeh, an Arab Israeli Knesset lawmaker who lives in Haifa, appeared on TV on Friday morning, criticizing those Israeli politicians and media who were blaming the fires on Palestinians.

"During this stormy day, I have been moving between different media, in an attempt to say this clearly: This is our home and it is our duty to preserve it. Now is the time for joint cooperation, to help evacuate the elderly and all those who need help," he wrote on Facebook.

Palestinian fire trucks sent to help

According to Magen David Adom, Israel's ambulance service, 35 people have been treated for light smoke inhalation across the country since the fires broke out earlier this week.

The Israel Defense Forces' Homefront Command has deployed two search-and-rescue battalions to assist civilian efforts.

The Palestinian Civil Defense provided eight fire trucks Thursday in response to an Israeli request for help, according to Nael Al-Azzeh of the Palestinian Civil Defense, based in West Bank city of Ramallah.

Palestinian firefighters working together with Israeli firefighters in the city of Haifa to help put out fires and blazes. pic.twitter.com/hfcoZd4TuO — Micky Rosenfeld (@MickyRosenfeld) November 25, 2016

Rosenfeld, the police spokesman, tweeted images of the Palestinian firefighters working alongside their Israeli counterparts in Haifa.

A large fire that blazed in Harashim, about 35 kilometers (22 miles) to the northeast of Haifa, was extinguished as of Friday afternoon.

More than 1,500 fires reported

According to Ran Sheluf, head of the investigation unit of the Israel fire and rescue services, more than 1,500 fires had been reported over the past week.

"This is twice the usual number," he said. "The cause of the fires is either negligence or being started deliberately."

To help battle the blazes, Netanyahu requested assistance from world leaders, including Russian President Vladimir Putin.

Russia is sending two giant Beriev Be-200 firefighting aircraft to assist with the operation after the two leaders spoke on the telephone.

Turkey, Italy, Croatia, Greece and Cyprus also are assisting Israeli authorities.

Italy's ambassador to Israel, Francesco M. Talo', tweeted images of Italian planes preparing to take to the air.

A specially adapted Boeing 747 called the Supertanker, owned by a private American firefighting business, is on its way to Israel.