President Barack Obama on Tuesday ordered about 350 more US troops to Baghdad to safeguard American diplomats in the Iraqi capital, increasing the U.S. military presence to more than 1,000 forces.

The move comes after a request last month from the State Department for additional U.S. troops to bolster security for the US embassy and other facilities in Iraq, where Islamic State (IS) extremists have seized territory in the north and west of the country.

U.N. Secretary General Ban Ki-moon said Wednesday the world was "outraged" at the apparent beheading of a second U.S. journalist in a video released by Islamic State (IS) militants.

"We are all outraged at reports from Iraq about the brutal killing of civilians by ISIL (IS), including yesterday's reported brutal beheading of another journalist," he said in New Zealand after a video purporting to show the death of US journalist Steven Sotloff was posted online.

Five Syrian pro-government activists have been arrested for criticizing the intelligence services and defense ministry over the loss of key military bases and the deaths of soldiers, an NGO said Tuesday.

Rami Abdel Rahman, director of the Syrian Observatory for Human Rights, said they were arrested on Friday "after criticizing the role of the defense ministry and the intelligence services in the loss of key bases in the north, particularly the Tabqa military airport."

British media on Tuesday voiced skepticism over "vague" plans announced by Prime Minister David Cameron to counter the threat of jihadist fighters traveling to Iraq and Syria.

Cameron said that among the measures envisaged was a plan to give border police powers to seize passports from departing would-be jihadists and restricting the movement of suspects.

Syrian warplanes pounded the rebel Jubar district of the capital Damascus with unprecedented ferocity on Tuesday, launching 25 raids, a monitor said.

"It's the largest number of air raids to hit Jubar since the beginning of the army offensive on the district" six days ago, said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.

A Chechen asylum seeker suspected of preparing to join Islamist guerrillas in Syria has been arrested in Austria, police said Tuesday, nearly two weeks after they detained nine others.

European countries have tightened controls over potential jihadists traveling to and from Syria and Iraq ever since Islamic State (IS) combatants overran large swaths of Iraq in June.

The World Food Program said on Tuesday that it provided food to a record 4.1 million people inside Syria last month.

The U.N. agency said it was able to reach more people because of a Security Council resolution adopted in July that authorized the movement of humanitarian aid to Syrians in rebel-held areas without government approval.

Al-Nusra Front is reportedly demanding Maronite Patriarch Beshara al-Rahi to apologize for the burning of an Islamic State of Iraq and the Levant flag by youth in Beirut's Ashrafiyeh district.

Sources close to the Muslim Scholars Committee said in comments published in the pan-Arab daily al-Hayat on Tuesday that “the group (al-Nusra Front) will not release the soldiers and policemen without anything in return.”

Fiji revealed for the first time Tuesday the demands being made by al-Qaida-linked Syria rebels who took more than 40 U.N. peacekeepers hostage in the Golan Heights last week.

Fiji army chief Mosese Tikoitoga said the rebels wanted their organisation, the al-Qaida affiliate al-Nusra Front, to be removed from the U.N.'s list of terrorist organisations.

Intense clashes erupted between the Lebanese army and gunmen on the outskirts of the northeastern border town of Arsal overnight Monday.

The state-run National News Agency said that rocket fire could be heard in Lebanon's Eastern Mountain Range, in particular, in the Sweid valley.