Airstrikes by Syrian jets and shells from tanks leveled a neighbourhood in a restive city near the capital of Damascus, reportedly killing 18 people, including four women and five children.
Tuesday's bombardment of the city of Douma, northeast of the capital, left residents scampering over a huge expanse of rubble and using their hands to dig up mangled bodies, according to activist videos posted online.
The army also fired mortar bombs into the Damascus suburb of Hammouria, killing at least eight people, activists said.
In Damascus city, Syrian fighter jet reportedly hit targets inside the capital for the first time on Tuesday, dropping four bombs on the neighbourhood of Jobar, near the opposition-held suburb of Zamalka, where rebel fighters were locked in fierce clashes with the army.
There were no reports of casualties in the bombing run, which AFP news agency correspondents said was heard across the capital.
Also on Tuesday, Syrian rebels claimed in an Internet statement they had assassinated an air force general in Damascus.
State television said that Major General Abdullah Mahmud al-Khalidi, was killed in the northern Damascus district of Rukn al-Din by "terroritsts".
The general, who it said was in charge of training, as well as an air force intelligence specialist, was shot dead on Monday evening as he left a friend's home, a security source in Damascus told AFP on condition of anonymity.
The violence came as Lakhdar Brahimi, the envoy appointed by the Arab League and United Nations, arrived in Beijing for a two-day visit, part of an attempt to secure support from Syria's allies before a visit to the UN Security Council next month.
Brahimi's scheduled talks with Yang Jiechi, foreign minister, follow a similar meeting with Sergey Lavrov, Russia's foreign minister, on Monday.
After that meeting, Brahimi said the civil war in Syria was growing even worse and that he was "terribly sorry" a ceasefire he had attempted to negotiate had failed.
Both China and Russia are allies of President Bashar al-Assad and have vetoed three Western- and Arab-backed resolutions at the Security Council condemning the Syrian regime for the violence. Both countries oppose any intervention in the war and have criticised others for interfering.
China had backed Brahimi's failed plan for a three-day truce that had been agreed by the Syrian government and the rebels last week, ahead of the Eid al-Adha holiday.
Russia and China have been scorned by the Gulf, the US and Turkey - a strong ally of the Syrian opposition which on Tuesday ruled out further dialogue with Assad's government.
"There is no point in engaging in dialogue with a regime that continues to carry out such a massacre against its own people, even during Eid al-Adha," Ahmet Davutoglu, foreign minister, said.
The ceasefire arranged by Brahimi was violated almost as soon as it was agreed, and both rebels and government troops initiated firefights after the holiday began at sunset on October 25.
Elsewhere in Syria on Tuesday, activists reported heavy fighting and air raids in the northern province of Aleppo, where they said rebels are surrounding an area where the headquarters of the air defence intelligence is located.
Activists also reported air raids for the second consecutive day on areas on the outskirts of Damascus.
Clashes on Monday left 130 people dead, according to the UK-based Syrian Observatory for Human Rights.
That violence included an explosion near a bakery in a southeastern district of Damascus controlled by forces loyal to Assad, killing at least 11 people, including children and women, and injuring scores, according to both activists and state news agency SANA.
A second explosion was reported in al-Hajar al-Aswad neighbourhood.
Activists there said an air raid by government forces struck a bus and left at least 10 people killed. State TV said it was a "terrorist" car bomb that left an unspecified number of victims.
The opposition claims at least 32,000 people have been killed since the uprising against Assad's rule began in March last year. Hundreds of thousands of people have fled to neighbouring countries.
In a televised interview after Monday's violence, Sheikh Hamad bin Jassim Al Thani, Qatar's prime minister, accused Assad's government of waging a "war of extermination" against its people
He told Al Jazeera that he also took issue with Brahimi's characterisation of the crisis.
"What is happening in Syria is not a civil war but a war of extermination against the Syrian people," he said.
In-depth coverage of escalating violence across Syria
The war, Sheikh Hamad said, was being waged "with a licence to kill, endorsed firstly by the Syrian government and secondly by the international community".
But he said Qatar still had faith in Brahimi, who is due to go to the Security Council in November with new proposals to push for talks between Assad and the opposition.
Brahimi said on Monday that the UN "is not considering" sending an armed peacekeeping force to Syria, though relevant officials were conducting contingency planning in case the Security Council ordered such a mission.
That is highly unlikely with Russia and China wielding vetoes.
Qatar, along with other Gulf Arab states, is widely believed to be funding and helping arm the rebels fighting Assad's forces. Media reports have also said that Turkey and the US are providing intelligence to assist those efforts.