Syrian government warplanes were in the air again on Saturday over the flash point northeastern city of Hasakeh, despite a US warning against new strikes that might endanger its military advisers. In another escalation of the five-year war, regime planes this week bombarded positions held by US-backed Kurdish forces in the city fighting Daesh (the so-called IS). The unprecedented strikes prompted the US-led coalition to scramble aircraft to protect its special operations forces helping the Kurdish fighters, warning the regime not to put the advisers on the ground at risk. It was apparently the first time the coalition scrambled jets in response to regime action, and possibly the closest call yet in terms of Syrian forces wounding American or coalition advisers. Throughout the night and into Saturday morning, regime warplanes took to the skies above Hasakeh again, according to the Syrian Observatory for Human Rights, a British-based monitoring group. It was not immediately clear whether the aircraft had carried out any bombing runs as there were heavy artillery exchanges on the ground. Deadly clashes erupted between pro-government militia and the US-backed Kurdish forces on Wednesday. The Observatory said there had been no let-up in the fighting, which has left 41 people dead, 25 of them civilians, including ten children. "There were heavy clashes, artillery fire and rocket attacks throughout the night and ongoing in the morning," Observatory head Rami Abdel Rahman said. Around two-thirds of Hasakeh is controlled by Kurdish forces, while the rest is held by pro-government militia. The regime and Kurdish forces share a common enemy in Daesh, which controls most of the Euphrates valley to the south, but there have been tensions between them in Hasakeh that have sometimes led to clashes. Thursday's government raids were the first time the regime bombarded Kurdish positions from the air. As soon as the strikes began, Kurdish ground forces unsuccessfully tried to hail the pilots via radio. US forces then contacted Russia, which has been bombing parts of Syria for nearly a year in support of President Bashar Assad, but Russian military officials said the planes were Syrian. Washington's decision to scramble its fighter jets "was done as a measure to protect coalition forces," Pentagon spokesman Captain Jeff Davis said. "We will ensure their safety and the Syrian regime would be well-advised not to do things that place them at risk... We view instances that place the coalition at risk with the utmost seriousness and we do have the inherent right of self-defense." But the Pentagon warning appeared to fall on deaf ears. Two Syrian regime warplanes attempted to fly to the area again on Friday, but left "without further incident" after meeting coalition aircraft, a US defense official said in a statement. "No weapons were fired by the coalition fighters." Davis said no coalition injuries were reported in Thursday's strike by two Syrian SU-24s, and US advisers were moved to a safe location. The coalition is now conducting additional combat air patrols in the region, he added. A Syrian military statement said the army had taken the "appropriate response" after Kurdish forces attacked Hasakeh. The Observatory said thousands of inhabitants had begun to flee the city, where bread was running out and electricity has been cut. A government source in Hasakeh said that the air strikes were "a message to the Kurds that they should stop this sort of demand," after Kurds called for the dissolution of a pro-regime militia. Washington regards the Kurdish People's Protection Units (YPG) as the most effective fighting force against Daesh in Syria and has provided them with air support as well as the military advisers. US special operations forces were based around 6 km north of Hasakeh and reinforcements arrived Friday "from inside and outside Syria, accompanied by military helicopters," Abdel Rahman said. Separately, two Russian ships in the Mediterranean launched long-range cruise missiles against militant targets in Syria on Friday, the Russian defense ministry said. The targets were linked to the former Al-Nusra Front, now Fateh Al-Sham Front, the ministry said. It was Moscow's first use of cruise missiles in Syria since December. More than 290,000 people have been killed since the conflict erupted in March 2011. In the central province of Homs, 20 civilians including at least five children died overnight in suspected regime air raids and artillery fire on a cluster of towns and villages, the Observatory said on Saturday.