Activist Yassin Abu Raed, from the town of Anadan in northern Aleppo province, has seen his house hit three times. The latest strike destroyed it completely.

"Death is all around us, and nobody cares," he said via the internet. "Barrel bombs kill those we love most, they destroy houses, dreams and memories, and leave us without any hope that the killing will ever stop.

"All this, and no one has even heard of us, no one feels for us."

The Observatory, which documents casualties and strikes, relying on a broad network of activists and doctors across the war-torn country, said at least 232 civilians have been killed in regime air strikes, including barrel bomb attacks, since October 20.

The Observatory said the number of barrel bomb attacks was "much higher" than a fortnight ago.

The government began using barrel bombs in late 2012, but stepped up its attacks this year, with a wave of raids in February alone killing hundreds of people.

On Wednesday, helicopters dropped four barrel bombs on a camp for displaced people in the northwestern province of Idlib, killing at least 10 people and wounding dozens, according to the Observatory. Activists posted horrific video footage on YouTube, showing bodies torn apart and people wailing as they tried to rescue survivors.

The United States denounced the attack as "barbaric".

Ismail al-Hassan, a volunteer nurse at a field hospital in Idlib province, said via the internet that health workers faced immense difficulties treating the wounded after a barrel bomb blast.

"Most of the casualties from barrel bomb strikes are women and children," said Hassan, adding that medical staff suffer from severe equipment shortages, making it hard to treat casualties properly.

In February, the UN Security Council passed a resolution demanding that all sides in Syria's war end attacks against civilians, with a specific mention of the use of barrel bombs.

The government denies using barrel bombs, and says it only targets "terrorists".

Lama Fakih, a researcher with New York-based Human Rights Watch, which has criticised Damascus over its "unlawful" use of barrel bombs, said: "While there is international effort to stop abuses by [the jihadist group] Islamic State, there is no concerted international effort to stop abuses by the Syrian government, including attacks against the civilian population."

Islamic State kills 85 more members of Iraqi tribe

Islamic State has executed 85 more members of the Albu Nimr tribe in Iraq, a tribal leader and security official said, part of a mass killing campaign launched last week to break local resistance to the group's territorial advances.

Tribal chief Sheikh Naeem al-Ga'oud said Islamic State had killed 50 members of Albu Nimr who were fleeing the group in Anbar province on Friday. A further 35 bodies were found in a mass grave, a security official said. Islamic State has executed a total of more than 300 tribe members in the past few days, Ga'oud and the official said.

The sustained bloodshed appears to demonstrate the group's resilience to the US air strikes that have been targeting its fighters in Iraq and Syria. Ga'oud said he had repeatedly asked the Shi'ite-led government in Baghdad for arms but that his pleas were ignored.

Albu Nimr had held out for weeks under siege by Islamic State, but finally ran low on ammunition, fuel and food. Hundreds of tribal fighters withdrew and the tribe fled its main village of Zauiyat albu Nimr, but many were intercepted and shot by the militants.