A pair of car bombs has killed at least six people and wounded several others in Syria's sprawling Rukban refugee camp near the border with Jordan, according to a rebel official and a resident.

The first explosion on Monday went off close to a restaurant, while the second targeted the camp's market nearby.

"There are at least six civilians dead and the number is expected to rise," Mohammad Adnan, a rebel official from Jaish Ahrar al-Ashair who runs the policing of the camp, told the Reuters news agency.

There was no immediate claim of responsibility.

In January, a car bomb killed a number of people in the camp, and the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) armed group has since launched attacks on Syrian rebels in the area.

Rukban, near the joint Syria-Iraq-Jordan border, is home to refugees and also to rebel groups, including the Jaish Ahrar al-Ashair, which fight both President Bashar al-Assad and ISIL.

It was also hit by bomb attacks last year.

The car bombs came just hours after air raids hit a Syrian border town in the eastern province of Deir Az Zor and killed at least 30 people, mostly civilians, according to a monitor, which tracks developments on Syria's conflict via a network of contacts on the ground.

The UK-based Syrian Observatory for Human Rights said that more than a dozen children were among those killed when the air raids - thought to have been carried out by the US-led coalition - hit residential areas and a mosque in the Abu Kamal town.

READ MORE: Syria's besieged communities

The ISIL-linked media outlet Amaq said coalition strikes killed 15 people and wounded 35 others in Abu Kamal.

ISIL holds most of Deir Az Zor province, apart from an enclave at the centre and a nearby air base controlled by Syrian government forces. The province links territory ISIL fighters control in Syria and Iraq.

Since it broke out in March 2011, Syria's conflict has killed hundreds of thousands of people, displaced millions and ravaged the country's economy and infrastructure.

Competing tracks of peace talks

A new round of Syria talks opens in Geneva on Tuesday, overshadowed by a competing process in Kazakhstan's capital, Astana, and with rebels reeling from a major setback in the capital, Damascus.

Efforts to end the war are now proceeding along two rival tracks: the formal political peace process hosted at the United Nations offices in Geneva and parallel talks in Kazakhstan brokered by Russia, Iran and Turkey.

Observers say the UN appears to be scrambling to match Astana's momentum after a landmark deal signed in Kazakhstan on May 4 to create four "de-escalation" zones across some of Syria's bloodiest battlegrounds.

UN special envoy Staffan de Mistura told reporters on Monday that the Geneva talks were working "in tandem" with the Astana process.

READ MORE: Can the 'de-escalation' plan in Syria work?

Since the Astana deal came into effect a week ago, fighting has slowed across swathes of the country.

But in Damascus, which is not included in the deal, the government has recently secured the evacuation of three rebel-held districts, bringing it closer to exerting full control over the capital for the first time since 2012.

Numerous rounds of UN-backed talks have not produced concrete results, although during the last round in March the sides finally began discussing four separate "baskets" of issues: governance, a new constitution, elections and combating "terrorism" in the country.