President Bashar al-Assad\'s forces hammered rebel positions Sunday with artillery and air strikes around Damascus, in a strategic assault aimed at securing the Syrian capital, a watchdog said. Shellfire from Syria, meanwhile, hit a Turkish border town late Saturday, withoutcausing any casualties. It was the first cross-border shelling since Ankara requested NATO deploy Patriot missiles along the restive frontier. Fierce fighting erupted in Irbin, a town east of Damascus, as troops also shelled Zabadani to the northwest of the capital and the village of Mliha, leaving many wounded, said the Syrian Observatory for Human Rights. Mliha, southeast of Damascus, is located in the region of Eastern Ghouta, where troops have launched a drive to secure the airport highway - scene of sustained fighting this week. Assad\'s forces have been trying to establish a secure perimeter around Damascus at all costs, turning the region into one of the main battlegrounds in the country\'s 20-month conflict. Analysts say the objective of the military campaign is to put the regime in a position to negotiate a way out of a conflict the Britain-based Observatory says has cost more than 41,000 lives since March 2011. In the north, the air force bombed the province of Aleppo, where ground troops have been locked in street fighting with rebels in Aleppo city for more than four months, said the watchdog. The area around Aleppo has also seen some heavy clashes the past few days, particularly since the rebels shot down two regime aircraft late last month. Fighting has been particularly fierce around the Damascus airport road this week. The 27-kilometre (17-mile) highway remained perilous Saturday a day after troops said they had reopened the link to the outside world in heavy fighting, the watchdog said. On Saturday troops were in action against rebels entrenched in both the southwestern outskirts of Damascus and the eastern suburbs where the airport lies, prompting the cancellation of a string of international flights. Southwest of the capital, the army staged new air strikes on key rebel positions such as the town of Daraya, where anti-regime sentiment is strong. Activists cited by the Observatory said the army deployed new forces to the town. \"Daraya will be secured in the coming hours,\" pro-regime daily Al-Watan said. Damascus has frequently declared battles are coming to an end, but such claims have rarely materialised as rebel resistance has proven hard to crack. \"The Syrian army has opened since Thursday morning the gates of hell to all those who even consider getting close to Damascus or of attacking the capital,\" Al-Watan added. After activists said the army was growing overstretched in flashpoints across Syria, the air corridor over Iraq has emerged as a supply route for weapons for the Assad regime, The New York Times reported. Citing unnamed US officials, the newspaper said that to the disappointment of the administration of President Barack Obama, US efforts to persuade the Iraqis to randomly inspect the flights have been largely unsuccessful. On the ground, tensions further flared up along the Turkish border after shells fired from Syria hit a Turkish border town late Saturday but caused no casualties, state-run Anatolia news agency reported. The shells landed near the town of Reyhanli amid clashes between Assad\'s troops and rebels around Syria\'s Bab al-Hawa border post with Turkey, Anatolia said. It was not immediately clear whether Turkish border forces struck back. Sunday\'s shells were the first to land in Turkish territory since Ankara officially requested from NATO last month the deployment of Patriot missiles along the border. NATO foreign ministers meeting Tuesday and Wednesday in Brussels are expected to signal support for Turkey by giving the go-ahead to deploy the missiles, diplomatic sources said.