At least 25 civilians, including children, were killed in the strikes early Thursday as fighting raged in parts of Hama, the Syrian Observatory for Human Rights said.
The Britain-based monitoring group said an alliance of rebel and jihadist forces launched an offensive on Monday in Hama, which is south of the opposition-held Idlib province.
The alliance, which includes the jihadist Jund Al-Aqsa force, is aiming to take control of the airport in Hama, from which regime helicopters fly regular sorties against opposition fighters.
"They are about 10 kilometres (six miles) from the airport" in Hama, Syria's fourth-largest city, said Observatory director Rami Abdel Rahman, whose group relies on a broad network of sources inside Syria.
The rebels are also likely seeking to ease pressure on opposition fighters in the battleground northern city of Aleppo by distracting regime forces.
In three days the rebel alliance seized control of 13 populated areas, mainly in the north of Hama province, including the towns of Halfaya and Suran.
They were also threatening the historic Christian town of Mahrada to the west along the road, which is home to one of the country's largest power stations.
Hama province is of vital strategic importance to President Bashar al-Assad, separating opposition forces in Idlib from Damascus to the south and the regime's coastal heartlands to the west.
Major demonstrations erupted in Hama in 2011 during the outbreak of Syria's conflict but were suppressed in a deadly government crackdown.
Assad's father and predecessor Hafez al-Assad brutally put down a Muslim Brotherhood uprising in Hama city in 1982, killing thousands.
In Aleppo city, residents in the city's rebel-held districts faced renewed shortages on Thursday as pro-regime forces continued to fire on the main supply road into their districts.
Markets were empty and fuel was scarce, an AFP correspondent in the city's opposition-controlled east said.
Aleppo has been roughly divided between rebel control in the east and government control in the west since mid-2012.
Areas south of the city have been the scene of intense fighting since July 31, when an alliance of rebel, Islamist and jihadist forces launched a major offensive to break a regime siege of its opposition-controlled districts.
It took the southern district of Ramussa on the city's outskirts early last month, linking up with opposition-held neighbourhoods and allowing food and medicine to be taken in.
But pro-regime forces have advanced in the past week, taking areas around the Ramussa road and firing at any vehicle on it.
Syria's conflict has killed more than 290,000 people and displaced millions.