The US has led airstrikes against Islamic State targets in Syria including the extremist group's stronghold of Raqqa, in the first direct military intervention by foreign powers since the start of the country's crisis.
Huge explosions shook Raqqa, the militants' capital in Syria, as fighter jets pounded the area and the northern province of Idlib. Unconfirmed air raids also hit the neighbouring provinces of Deir al-Zour and Aleppo, according to local reports.
Several Gulf states partnered the US in the 14 airstrikes, which were conducted using fighter and bomber jets and Tomahawk missiles following last week's international talks on combating the Islamist fighters.
The Pentagon later released a set of weapons system videos showing footage of a selection of the strikes that were carried out. The video was taken by cameras onboard the aircrafts.
According to information provided on the US Central Command's YouTube channel, the video below shows a strike by a US aircraft on an Islamic State storage facility near Abu Kamal, Syria.
A second video shows a strike on vehicle staging point, also near Abu Kamal.
A third video shows a strike on an Islamic State compound reportedly northwest of Raqqa.
Saudi Arabia, Jordan, Bahrain, Qatar and the UAE all "participated in or supported" the attacks, the Pentagon confirmed. Spokesman Rear Admiral John Kirby said that "US military and partner nation forces are undertaking military action against ISIL terrorists in Syria using a mix of fighter, bomber and Tomahawk Land Attack Missiles."
The US has already carried out around 190 air strikes on Islamic State fighters in Iraq and Barack Obama has been under pressure to extend such attacks to Syria, where the group has carved out large swathes of territory including key oil fields as it seeks to establish an Islamic caliphate across the two countries.
As the airstrikes took place, the Islamic State released a second video featuring the kidnapped British journalist John Cantlie, in which the hostage delivered a statement claiming the US-led coalition was walking into a "Vietnam" in the Middle East.
Cantlie said Western governments were "hastily marching to all out war in Iraq and Syria without paying any heed to the lessons of the recent past." The statement characterised the Islamic State as "the most powerful jihadist movement seen in recent history" and denied it could be destroyed by current Western efforts, insisting "this is not some undisciplined outfit with a few kalashnikovs."
"That the western govs were caught napping by the sheer speed of the Islamic State's growth is now a given," Cantlie said. "It's all quite a circus — airstrikes, the creation of last minute puppet governments, advisory teams on the ground, wooing previous enemies to join in and trans-border incursions into a country that has been in a state of civil war for three years, all the while underestimating the strength and fighting zeal of the opponent. Not since Vietnam have we witnessed such a potential mess in the making."
France meanwhile confirmed that a French tourist, Herve Gourdel, had been seized in Algeria by the militant group Jund al-Khilafa, which threatened to kill the 55-year-old if if Paris did not cease the airstrikes it began on Friday in Iraq. Islamic State fighters warned on Sunday they would target Western citizens in retaliation for such actions, "especially the spiteful and filthy French".
Western powers have been hesitant to intervene in the Syrian conflict, with Washington pulling back from intervention following chemical attacks on civilians last year despite having previously warned the Assad government that the use of such weapons constituted a red line. The West and its allies have channeled weapons and other forms of military support to moderate rebels fighting Assad but concerns about such arms falling into the hands of Islamist extremists have complicated efforts.
President Bashar al-Assad has been keen to convince the international community that it is the Islamic State and other jihadist groups, rather than his regime, which pose the greater threat — and as Western fears over IS advances in Iraq and Syria grow, the tide appears to be turning in his favour as the perceived lesser of two evils.
The Syrian foreign ministry said it was informed about the strikes before they took place. "The foreign minister received a letter from his American counterpart via the Iraqi foreign minister, in which he informed him that the United States and some of its allies would target (Islamic State positions) in Syria," the department said. "That was hours before the raids started."
Foreign ministry statements flashed across Syrian state television as the airstrikes went on. "Syria supports any international effort that aims at fighting terrorism, whatever the terrorist group - IS, al-Nusra Front or any other one," one said, according to BBC Monitoring. Another added: "Syria will also continue fighting IS in Raqqa and other districts and will not stop fighting the group in cooperation with states which are directly harmed, principally Iraq."
The country's Western-backed National Coalition opposition group welcomed the strikes by the US and Arab allies, saying they would aid the rebels in their battle against the government.
"This will make us stronger in the fight against Assad… The campaign should continue until the Islamic State is completely eradicated from Syrian lands," Monzer Akbik, special envoy to the coalition leadership, told Reuters.
An Islamic State fighter meanwhile insisted the group would have its revenge for the attacks, and held Saudi Arabia responsible for allowing them to go ahead.
"These attacks will be answered. The sons of Saloul are the ones who are to be blamed. It happened because of them," he told using a derogatory term for Saudi Arabia's royal Saudi family.
One resident of Raqqa apparently live-tweeted the strikes in the area as they happened, reporting "huge explosions" half an hour before the raids were announced by the US military.
The airstrikes 5/6 concentrated near the 'governorate building' ISIS's main HQ. Meanwhile, sounds of warplanes can be heard clearly
— Abdulkader Hariri (@3bdUlkaed6r)September 23, 2014
UK-based monitoring group the Syrian Observatory for Human Rights said a number of the strikes had killed civilians as well as Islamist fighters. It noted that in Raqqa and surrounding areas IS fighters had already evacuated the majority of their command centres. The group had reportedly been preparing their defenses in anticipation of airstrikes in recent days, sending women and children out of Raqqa and dispersing fighters into civilian neighborhoods.
Syrian refugees have been flooding to the Turkish border in recent days as Islamic State fighters advance on the key Kurdish town of Kobane. Turkish forces have clashed with Kurdish protesters rallying in support of the Syrian arrivals and reportedly trying to cross the border into Syria to fight the Islamist group.
On Tuesday, refugees at a border crossing near Kobane told VICE News that IS fighters had pulled back from the city following the night's airstrikes.
One man, who gave his name as Ahmed Kobane, said "Kobane is empty, there's no food, no water, no anything. We will wait here and maybe things will return to normal."
Another, 30-year-old Mustafa Muslim, said: "The US and Europe should have hit IS in Syria a month ago. Now, they're late."
Additional reporting by John Beck
Follow Hannah Strange on Twitter: @hannahkstrange
Follow John Beck on Twitter: @JM_Beck