Bomb attacks in Syria's capital Damascus and the country's south killed at least 16 people on Wednesday, a day after Moscow and Washington failed to announce a date for proposed peace talks.

In Russia, Deputy Foreign Minister Mikhail Bogdanov said Moscow was ready to host informal talks between Syrian President Bashar al-Assad's regime and the opposition.

Russian and US officials on Tuesday failed to agree a date for a proposed peace conference in Geneva that has been delayed multiple times.

On the ground in Syria, at least eight people were killed and 50 wounded in Damascus by a blast in the central Hijaz Square, state news agency SANA reported.

"Eight citizens including two women were killed in an explosion caused by a bomb placed by terrorists at the entrance to the Hijaz railroad company," SANA said, using the regime's term for rebels.

And in the southern city of Sweida, eight intelligence officers were killed in a suicide car bomb that went off by their facility, the Syrian Observatory for Human Rights said.

"A suicide attacker detonated himself in a car bomb in front of the air force intelligence headquarters in Sweida, killing the intelligence branch chief and seven other officers," Observatory director Rami Abdel Rahman said.

The city is a bastion of the Druze minority and is under regime control.

SANA also reported the attack, citing a police source who said "eight citizens" were killed and 41 others injured.

In central Homs province, the Observatory reported that rebels had seized part of a key arms depot, two weeks after they launched an offensive aimed at the facility, near Mahin in the countryside.

Fighters from Al-Nusra Front and ISIL -- both linked to Al-Qaeda -- and the Al-Khadraa and Baba Amr battalions "took over buildings of an army weapons depot near Mahin," the group said.

The rebels "seized a large amount of weapons" in the complex, which comprises some 30 buildings, it added.

But a regime security official denied the report, saying: "The battle is continuing. The terrorists did not take any weapons, and there are many losses in their ranks."

The fighting has been fierce at times, with more than 50 rebel fighters and 20 loyalists dead on Tuesday alone, according to the Observatory.

In northern Aleppo province, the monitoring group said regime forces had seized control of most of Tal-Aran town, strategically located on the main road between the city of Aleppo and town of Sfeirah.

Sfeirah is near a military site believed to hold some of the regime's chemical weapons, and was recaptured by the army last week.

The group also reported that ISIL fighters took control of the nearby Aleppo power plant on Wednesday, raising fears it could cut electricity to parts of the city.

Only regime-held parts of Aleppo still receive power from the plant.

'Statue of Liberty' decapitated

And in the northern city of Raqa, the only provincial capital under rebel control, the Observatory said ISIL fighters had executed a local doctor, accusing him of being a spy for Turkish intelligence.

ISIL fighters also decapitated a statue depicting a male and female peasant, known locally as the Statue of Liberty, said the Observatory, which takes its information from activists and doctors on the ground.

The latest upsurge of violence came a day after Washington and Moscow failed to announce a date for proposed Syria peace talks.

UN-Arab League peace envoy Lakhdar Brahimi told reporters in Geneva he was still hopeful the conference could be held before year's end.

The United States and Russia have been pushing for peace talks in Geneva for months, but Brahimi said divisions within the Syrian opposition were an ongoing obstacle to a conference.

Much of Syria's opposition opposes talks with the regime and wants Assad's departure to be a condition of any conference, which the Syrian government rejects.

On Wednesday, the main opposition National Coalition said recent statements by officials "expose the regime's paralysis with regards to any political solution".

Information Minister Omran al-Zohbi said Monday that the regime will not attend if the aim is for Assad to hand over power.

More than 120,000 people have been killed in Syria's 31-month conflict, which began when Assad's regime cracked down on anti-government protests.