Syrian war planes bombed rebel positions north of Aleppo Tuesday near contested air force bases.
The bases fall between Aleppo and supply routes to Turkey, making them strategically important for the embattled rebels.
Heavy clashes were also reported in Aleppo, Syria's largest city, Tuesday but there were no reports yet of casualties.
"Right now the Syrian government is fighting for control of strategic points. They have been significantly strengthened by the addition of Hezbollah fighters and also the shabiha militia forces," Kirk Sowell, principal of Uticensis Risk Services, a political risk firm, told GlobalPost.
"They are trying to regain control of the Mang Air Force Base, and appear to be focusing on the towns of Anadan and Hraytan, which are located five to six miles north of Aleppo city proper."
Air power has also been an important factor in recent gains for the Syrian government, and has limited the territorial advancements of the rebels during the two-year battle.
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On June 10, the Syrian government announced that it was commencing "Operation Northern Storm" to retake Aleppo.
The operation was expected to commence within days of the announcement but so far the fighting has been concentrated in areas around the city.
The recent fighting also comes amid a statement by the G8 Tuesday, currently meeting in Northern Ireland, that sought to find a common position on events in Syria despite disagreements.
British Prime Minister David Cameron said in a news conference that he does not see a future for Syrian President Bashar al-Assad in Syria.
Despite his remarks, the G8 released a seven-point plan for Syria that does not mention the removal of Assad, no doubt due to Russian objections.
The plan includes 1) increasing the G8's commitment to humanitarian aid, 2) maximizing the diplomatic pressure on Syria to bring all sides to the table as soon as possible, 3) backing a "transitional governing body" for Syria, 4) learning the lessons of Iraq, 5) maintaining Syria's public institutions, 6) working together to "rid Syria of terrorists and extremists, and 7) condemning the use chemical weapons while allowing for a United Nations probe.
More from GlobalPost: Operation Northern Storm: Syrian army plans assault on Aleppo
Below is an unverified video purportedly showing rebels bombing the Kweiras air base in northern Syria:
Another video purporting to show the destruction of a Syrian government tank during fighting on June 18, 2013: