A Dutch citizen suspected of having trained in a jihadist camp in Syria has been arrested at Lisbon airport carrying a knife, Portuguese news media reported Sunday.

The 29-year-old man, born in Angola, was apprehended while trying to sneak aboard a passenger plane operated by Angolan airline TAAG, the Correio da Manha newspaper said.

The jihadist Islamic State group has expelled more than 30,000 people from their homes in the eastern Syrian town of Shuheil, a monitoring group said on Sunday.

The Syrian Observatory for Human Rights said IS had "forced out" some 30,000 residents after seizing Shuheil on Thursday from al-Qaida affiliate al-Nusra Front.

Syrian jets fired shells at the eastern Bekaa region of Arsal on Sunday, reported the National News Agency.

It said that they targeted Syrian gunmen in Wadi al-Khail in Arsal.

The Islamic State (IS) jihadist group which spearheaded a sweeping militant assault that overran swathes of Iraq is now claiming leadership of the world's Muslims.

Known for its ruthless tactics and suicide bombers, IS has carried out frequent bombings and shootings in Iraq, and is also arguably the most capable force fighting President Bashar Assad inside Syria.

Eight members of a single family were killed on Saturday when Syrian aircraft dropped explosive-packed barrel bombs on a town in the southern Syrian province of Daraa, a monitor said.

The Syrian Observatory for Human Rights said a man, his wife and their six children were killed in the raid in the town of Dael.

Abu Bakr al-Baghdadi, the enigmatic self-proclaimed "caliph" of a state straddling Iraq and Syria, is increasingly seen as more powerful than al-Qaida's chief.

The leader of the powerful Islamic State (IS) militant group was on June 29 declared "caliph" in an attempt to revive a system of rule that ended nearly 100 years ago with the fall of the Ottoman Empire.

Self-proclaimed caliph Abu Bakr al-Baghdadi made an unprecedented appearance in the Iraqi city of Mosul, which his forces captured last month, ordering Muslims to obey him, according to a video posted Saturday.

That marks a significant change for the shadowy jihadist whose Islamic State (IS) group led a lighting offensive that has overrun swathes of five provinces north and west of Baghdad.

Sunni Muslim religious scholar Yusef al-Qaradawi said on Saturday that the declaration of an Islamic caliphate by jihadists fighting the governments in Syria and Iraq violates sharia law.

Last Sunday, the jihadists declared an "Islamic caliphate" in areas they control in Iraq and Syria and ordered Muslims worldwide to pledge allegiance to their leader Abu Bakr al-Baghdadi.

Militants may have overrun large swathes of Iraq and he might face eroding domestic and international backing, but Prime Minister Nuri al-Maliki remains many Iraqis' top choice to lead the country.

Experts have cast doubt on the incumbent's chances of keeping his post as factions struggle to form a government after April polls, but sectarian allegiance may yet rescue the Shiite Arab leader, and a brutal onslaught by Sunni militants might have even strengthened his supporters' resolve.

Social Affairs Minister Rashid Derbas denied on Saturday any rift with Foreign Minister Jebran Bassil, stressing that the cabinet had agreed to establish camps for Syrian refugees outside Lebanese territories or in buffer zones along the border with Syria.

Derbas ruled out in remarks published in local newspapers the differences with Bassil over the appropriate ways to resolve the crisis.