The strikes late Wednesday and early Thursday hit at least five towns in Idlib and Aleppo provinces.
One video purportedly filmed after an airstrike Thursday on the Idlib city of Maarent al-Numan shows a man holding up two child-sized legs not connected to a body. Another man walks by carrying an arm.
Yet another video shows 18 white cloth bundles holding the remains of those killed.
Other videos from the city of Aleppo show the aftermath of an airstrike on a mosque late Wednesday. While some men carry away bodies, others work to dig out a survivor whose legs are buried in debris.
Activist claims and videos cannot be independently verified due to restrictions on reporting in Syria. But all videos corresponded to activist reports and appeared to have been filmed where they said they were.
The footage provides a window into the carnage wrought by the Syrian military's increasing reliance on airstrikes to fight rebels waging a harsh civil war to topple President Bashar Assad.
Rights groups say the airstrikes often hit civilian areas. And this week, Human Rights Watch accused Syria of using cluster munitions, which the New York-based group says endanger civilians.
The regime contends that it is fighting terrorists backed by foreign powers who seek to destroy Syria. It also denied using cluster munitions.
An Aleppo-based activist who gave his name as Abu Raed said men were arriving for Wednesday evening prayers when a fighter jet dropped a bomb on the Light of the Martyrs Mosque in the Shaar neighborhood.
The blast destroyed a room used for ritual washing and part of the prayer hall itself, he said via Skype.
He said at least 10 people had been killed, though the number could be higher, either because bodies were still trapped in the rubble or because people were buried before being recorded.
"There were people who took the dead and wounded away before the cameras showed up," he said.
Videos that activists said were shot soon after the attack show a block-wide expanse of rubble surrounded by buildings whose facades had been blown off. Men scour the rubble, occasionally finding bodies and carrying them off.
Rebels and regime forces have been clashing for months in Aleppo, Syria's largest city.
Regime aircraft also pounded Maaret al-Numan and surrounding areas on both days. The area has seen heavy fighting since rebels seized the city last week.
One strike hit a neighborhood near the rebel field hospital on Thursday in Maaret al-Numan, Yassin said via Skype.
He said it was too early to know how many people had been killed. A video posted online later showed 18 white cloth bundles activist said contained the remains of those killed.
Airstrikes also hit three nearby villages on Wednesday, killing 15 people, said activist Fadi Yassin. Nine of those were in Kafar Nubul, while others died in the villages of Kafrouma and Hass.
Rebel brigades from the surrounding area have poured in to defend the town, which stands along the main highway linking Aleppo to other large Syrian cities further south.
Online videos have shown them firing mortars at regime troops, and they claimed to have shot down a government helicopter on Wednesday.
As a sign of how little months of international diplomacy has done to stop the bloodshed in Syria, a number of nations and the U.N. envoy to the Syria conflict are pushing for a temporary cease-fire during a Muslim holiday later this month.
Joint U.N.-Arab League envoy Lakhdar Brahimi has called on the Syrian government to take the first step in observing a truce during the four-day Eid al-Adha holiday that begins on Oct. 26.
In Amman, Jordan, on Thursday, he said the temporary truce could be a first step in helping Syrians "to resolve their problems and to rebuild a new Syria as aspired for by its people."
The Syrian government said it wants a cease-fire but the rebels lack a unified leadership that can agree to it.
Both sides have flouted previous cease-fires after verbally agreeing to them.
On Thursday, Iranian President Mahmoud Ahmadinejad called for the truce during a visit to Kuwait.
The Iraqi government also expressed its support in a statement, calling on all sides to abandon violence "to save the region from more miseries and pains."
Activists say more than 33,000 people have been killed since the anti-Assad uprising started in March 2011.
Also Thursday, Syria's state news agency said rebels blew up two oil and gas pipelines in the northeast near the Iraqi border.
The agency, SANA, said the attack hit one oil and one gas pipeline Thursday near the city of Deir al-Zour. The pipelines ran between Deir al-Zour and the city of Palmyra in central Syria.
SANA quoted an oil ministry official saying the lines were immediately shut off, the fires were extinguished and repairs would begin soon.
Rebels have repeatedly bombed such pipelines.
Associated Press writers Ali Akhbar Dareini in Tehran, Iran, Jamal Halaby in Amman, Jordan, and Sameer N. Yacoub in Baghdad contributed reporting.