The Syrian Network for Human Rights said its casualty toll included 11 children and nine women.
The London group said 13 members of the Fatouh family burned to death in their home in the village of al-Bayda.
The group said 14 people were killed when shelling hit the main market in Areha of Idlib.
Ninety-six of the 185 people killed Sunday were in Damascus and surrounding countryside, the network said.
British Prime Minister David Cameron said his country is unlikely to send military aid to Syrian rebels because of the increasing presence of Muslim extremists.
In an interview with the BBC this weekend, Cameron conceded the rebellion in Syria was stalemated and "on the wrong trajectory," but his government's response would continue to be limited to non-lethal supplies.
"What we should be doing is working with international partners to help the millions of Syrians who want to have a free democratic Syria, who want to see that country have some form of success," Cameron said.
The prime minister's concerns were illustrated Sunday by an announcement from inside Syria that Kurdish rebels had captured a senior al-Qaida member.
The Kurdish People's Defense Units (YPG) posted on its Twitter account a photo of the captured terrorist identified as Abu Musab, the amir of the Islamic State of Iraq and the Levant, (ISIS), Israel Radio and Arutz Sheva reported Sunday.
Musab was reportedly grabbed in an area of northeast Syria, where intense fighting between the Kurds and al-Qaida operatives has occurred in recent days, the radio said.
Concerns that radical Islamist groups held too much sway among the opposition forces has been cited as a reason for Western powers to ship in heavy weapons needed to counter the armor and air power of President Bashar Assad. Assad, who has been bolstered by aid from Iran, Russia and Hezbollah, has seemed to swing the momentum to his side.
But Cameron described the situation as a stalemate," It is a very depressing picture and it is a picture which is on the wrong trajectory," Cameron said.
He added, however, that London was still committed to helping the rebels oust Assad and establish a new government. "You do have problems with part of the opposition which is extreme, that we should have nothing to do with," he said. "But that is not a reason for pulling up the drawbridge, putting our head in the sand and doing nothing."
The Guardian said Cameron discounted speculation his wife Samantha, an ardent advocate for Syrian refugees stuck in camps in neighboring countries, was pressuring him to take a more-active approach to ending the conflict. He referred to the idea as "a total urban myth."
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