The toll from two alleged Islamic State group car bombings overnight of rebels in Syria's Aleppo province has risen to at least 32 people, a monitor said on Wednesday.

Three local commanders were killed in one of the attacks, the Syrian Observatory for Human Rights said, describing the incidents as an apparent IS attempt to expand in the northern province.

The cabinet tasked on Wednesday Agriculture Minister Akram Shehayeb with following up on the case of Lebanese drivers who have been stranded on the Syrian-Jordanian border since last week.

Information Minister Ramzi Jreij said that Shehayeb will hold contacts with the Jordanian and Saudi Arabian embassies to discuss the matter.

Syria said Wednesday a military operation was needed to expel jihadists who have overrun large parts of a Palestinian refugee camp in southern Damascus, trapping thousands of civilians inside.

The Islamic State group's advances in the Yarmuk camp have sparked international concern for the civilians, who have already endured repeated bombardment and an army siege of more than 18 months.

Spanish police Wednesday arrested 11 people suspected of links to the Islamic State group, including six Muslim converts, some of whom intended to launch attacks in the Catalonia region, officials said.

It was the latest of scores of such raids as Europe seeks to stop recruitment by the extremist group, which has claimed the killings of many foreign hostages.

Syria said Tuesday it is ready to offer Palestinians its firepower to support their battle with the Islamic State group in a refugee camp devastated by clashes and aerial attacks.

The deteriorating humanitarian situation in the Yarmuk camp has pushed the U.N. Security Council to demand greater access to residents trapped between the encroaching IS jihadists and besieging government forces.

A Syrian man living in Britain described as a prominent activist opposed to President Bashar Assad was found shot dead in his car in north-west London, the BBC reported Wednesday.

Police were called by paramedics after a man was found with what were thought to be bullet wounds to the chest, the broadcaster said.

British police said Tuesday they were investigating a report that two teenagers, who come from the same town as one of the 2005 London suicide bombers, may have joined Islamic State jihadists in Syria.

The two 17-year-olds from Dewsbury in northern England are believed to have boarded a flight from Manchester to Dalaman in southwest Turkey on March 31, the regional police force said in a statement.

Syrian authorities on Tuesday arrested a member of the domestic "tolerated" opposition as he returned to the country from a rights meeting in Geneva, a monitor and an activist said.

"The opposition figure and human rights activist Saleh al-Nabwani was arrested on Tuesday on the Lebanese-Syrian border," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

The EU's top immigration official on Tuesday said the bloc was "concerned" by its existing asylum regulations and was looking at ways to amend them with large numbers of migrants fleeing conflict crossing the Mediterranean.

"I know the Greek government is concerned by (the regulations) -- the European Commission is also concerned," European migration commissioner Dimitris Avramopoulos said during a visit to Athens.

The U.N. Security Council has demanded humanitarian access to Syria's Yarmuk Palestinian refugee camp as residents described fleeing in terror after the arrival of jihadists of the Islamic State group.

The advance by the extremists into the battered neighbourhood of south Damascus has alarmed the international community and Palestinian officials, with a delegation from the West Bank heading to Syria to discuss the situation.