The Syrian regime has carried out indiscriminate and sometimes deliberate air strikes against civilians which have killed at least 4,300 people since last summer, an international human rights group said.
Human Rights Watch said Syrian fighter jets have deliberately targeted bakeries, bread queues and hospitals in the country's northern region.
Parts of northern Syria - especially areas along the border with Turkey - have in the past months fallen under the control of rebels fighting to topple President Bashar Assad, including several parts of the northern city of Aleppo, which is the country's largest urban centre.
"The aim of the air strikes appears to be to terrorise civilians from the air, particularly in the opposition-controlled areas where they would otherwise be fairly safe from any effects of fighting," Ole Solvang, of the New York-based group, said.
Mr Solvang led the HRW team which inspected 52 sites in northern Syria and documented 59 unlawful attacks by the Syrian air force. At least 152 people were killed in these attacks, according to an HRW report.
In most of the strikes, the regime planes appear to have had no military target in sight, such as armed opposition supporters or rebel headquarters, when they dropped their weapons on civilian areas, the group said.
The 80-page report said that, across Syria, more than 4,300 civilians have been killed in attacks by Assad's jets since last July.
The HRW report is the most comprehensive study of Syrian air force operations since last summer, when Assad's forces started to rely heavily on fighter jets to repel rebel advances and reverse their territorial gains.
The opposition now controls large swathes of northern Syria, and last month captured their first provincial capital, the city of Raqqa. The opposition fighters also control whole districts of Aleppo, and some key infrastructure in the east, including oil fields and dams on the Euphrates river.
With the recent influx of better weapons and other foreign aid, the rebels have also made major gains in the south, seizing military bases and towns in the strategically important region between Damascus and the border with Jordan, about 100 miles from the capital. The opposition fighters hope to eventually storm Damascus from the south.