At least 27 people have been killed and dozens injured after a Syrian fighter jet crashed into a marketplace in the rebel-held town in north-west Syria, witnesses said.The UK-based Observatory for Human Rights, which tracks violence across Syria, said most of the dead were civilians in Ariha, which fell to a coalition of Islamist insurgents in May. Scores were also injured, according to the observatory and witnesses. There was no immediate reaction from the Syrian army. The military plane bombed the centre of the town, which is in Idlib province, before crashing in the middle of the marketplace on Monday, witnesses told Reuters. “The plane had dropped a bomb on the main bazaar street at low altitude only seconds before it crashed,” said Ghazal Abdullah, who was close to the incident. The observatory said the jet was not shot down. Facebook Twitter Pinterest A photo provided by a Syrian anti-government activist group shows parts of a destroyed regime warplane that crashed in Ariha. Photograph: APFighting has intensified recently in Idlib province between government forces and an insurgent grouping called Jaish al-Fateh (Army of Conquest) which includes al-Qaida’s Syrian wing Nusra Front.The fall of Ariha has left the insurgents in control of most of Idlib, which borders Turkey and neighbours Latakia province, the heartland of President Bashar al-Assad’s Alawite sect, on the Mediterranean coast. Most of the rich agricultural region, however, has since come under heavy aerial bombardment by Assad’s forces in a counter-offensive to regain lost ground.The Syrian army has also used air strikes in an effort to halt insurgent advances into Latakia province. Those advances have brought rebel forces closer to government-held coastal areas north of the capital, Damascus. Syria’s western flank, which fringes both the Mediterranean and the Lebanese border, also contains the country’s other the major cities and is seen as crucial for Assad’s hold on power.Syria’s civil war began in March 2011. The United Nations says more than 220,000 people have been killed and at least a million wounded in the war.