BEIRUT (AP) — Rebels shot down a Syrian military helicopter in northern Syria on Tuesday, killing its crew members in a fiery crash, while the government kept up its relentless bombing campaign on the opposition-held region, with an airstrike in which seven civilians died, activists and news reports said.

The violence in Idlib province came as government troops moved closer to capturing the last rebel-controlled section of a strategic highway linking southern and northern Syria, which would bring the road under the full control of President Bashar Assad’s forces for the first time since 2012.

With support from Russia and Iran, Syrian troops have been on the offensive for weeks in Idlib and parts of nearby Aleppo provinces, unleashing a humanitarian crisis with 700,000 people fleeing their homes and surging north toward the Turkish border.

Nearly a quarter of the 3 million people in Idlib and nearby areas have fled. Terrified families piled onto trucks and other vehicles, clogging muddy rural roads in yet another harrowing exodus in the conflict, now in its ninth year. Hundreds of civilians have died in the latest fighting, according to the United Nations.

The Syrian helicopter gunship was shot down by insurgents amid fighting near the village of Nairab as rebels, backed by Turkish artillery, tried to retake it after losing it last week, according to opposition activists.

Associated Press video showed the helicopter spiraling from the sky and breaking up as fire poured from its fuselage, just before it crashed. Two bodies could be seen on the ground.

Turkey’s official Anadolu news agency reported that the pilot and two others aboard were killed, while opposition activists reported that only two crew members were on board.

Hours later, a Syrian airstrike hit the city of Idlib, the provincial capital, killing seven people and wounding nearly two dozen, according to the Syrian Civil Defense, also known as White Helmets. The Britain-based Syrian Observatory for Human Rights said the airstrike killed 12 civilians, half of them children, and wounded about 30.

Opposition activists said the airstrike on Idlib, home to about 800,000 people, was carried out in response to the downing of the helicopter.

The fighting recently escalated with two separate clashes between Syrian and Turkish troops, killing 13 on each side, including five Turkish soldiers who were killed Monday.

Turkey, a main backer of the rebels, has rolled armored vehicles into Idlib, apparently to prevent government forces from reaching the border areas with Turkey. The country is home to some 3.6 million Syrian refugees and is concerned about more streaming in.

Turkey’s defense minister told The Associated Press that Ankara has as many as four observation posts and two military positions in Syrian government-controlled territory, warning that Turkish soldiers were under orders to retaliate forcefully to any attacks.

Defense Minister Hulusi Akar said in the interview that Turkey would not vacate any of its 12 observation posts in Idlib.

“In the event of any action against them, they have been given instructions to retaliate even more powerfully,” he said.

The Turkish Defense Ministry tweeted that more than 50 Syrian government troops were “neutralized” in Idlib province, without giving details of the circumstances. The claim could not be independently verified and military officials could not immediately be reached for comment.

The Syrian army said the Turkish threats “will not dissuade the (Syrian) army from continuing its operations in Idlib and western Aleppo province to cleanse them of terrorism.” It warned that the military is ready to respond to the “aggression of Turkish occupiers.”

Turkish President Recep Tayyip Erdogan also warned Assad’s government that it will “pay a very, very heavy price” for attacks on Turkish troops.

At a speech in Ankara, he said he would explain Turkey’s next steps in Idlib province at a ruling party meeting Wednesday.

During a trip to Montenegro, Turkish Foreign Minister Mevlut Cavusoglu urged Russia and Iran to halt “the regime’s aggression.”

He said the offensive in Idlib was threatening Turkey’s relations with Russia.

“There have been very important results from our cooperation, but unfortunately the regime’s attacks in Idlib, killing civilians and attacking our troops, have begun to do a great deal of damage to this partnership,” he told a news conference.

Cavusoglu added that Erdogan and Russian President Vladimir Putin would talk by telephone.

Talks between Russian and Turkish officials about the escalation in Idlib ended Monday. Erdogan’s office said the Russian delegation was told that attacks on Turkish posts in Idlib must stop immediately and promised to retaliate to further attacks.

The Observatory reported that Syrian troops have secured the highway that starts in southern Syria, near the border with Jordan, and runs all the way north to the city of Aleppo. Its capture is vital for Syria’s economy as well as for moving troops.

An unidentified Syrian military official was quoted by pro-government media as saying that they still have to capture five villages before securing the highway, known as the M5.

The highway’s capture will mark another victory for Assad, whose forces have been making solid gains since the end of 2015 with the help of Russian airstrikes and Iran-backed fighters.

For the past three years, government forces have been capturing parts of the 450-kilometer (280-mile) highway that links the country’s four largest cities.

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Fraser reported from Ankara, Turkey. Associated Press writer Andrew Wilks in Ankara contributed.