British lawmakers are expected to vote Friday to join the international air strikes against Islamic State fighters, as the United States and its Arab allies turn up the heat on the jihadists.
In Washington on Thursday, the Pentagon released cockpit video of guided missiles from F-15 jets smashing into oil refineries and Islamic State compounds in the latest night of strikes in Syria.
US President Barack Obama took advantage of the UN General Assembly in New York this week to bend the ears of fellow world leaders over the threat posed by the jihadists.
The group has seized a large tract of territory spanning eastern Syria and northwestern Iraq, and has begun to make headway inspiring Islamists further afield to pledge fealty to its "caliphate".
British lawmakers will vote Friday on whether to bomb Islamic State militants in Iraq, though not in Syria.
"We are facing an evil against which the whole world must unite. And, as ever in the cause of freedom, democracy and justice, Britain will play its part," Prime Minister David Cameron told a United Nations summit in New York, before flying home for the vote.
Cameron has urged Britain not to be "frozen with fear" about re-entering conflict in a country its last troops from the previous war left only in 2011.
French jets were in action again on Thursday in the skies over Iraq.
The US-led coalition has also made progress in building a united front. Turkey has pledged stronger support for the campaign, and Obama spoke to President Recep Tayyip Erdogan on Thursday.
If, as expected, the British parliament votes to take part, the Royal Air Force will join jets from the United States, France, Saudi Arabia, the United Arab Emirates, Bahrain and Jordan hitting IS targets.
Belgium and the Netherlands said they would each send six F-16 fighter bombers to take part in the air campaign in Iraq.
The Netherlands will also deploy 250 military personnel and 130 trainers for the Iraqi military, and Greece said it would send arms to Kurdish forces battling the jihadists.
In all more than 50 nations have joined the US-led coalition against IS, including key Arab states, and in recent days more countries have promised concrete military support.
And the allies' domestic intelligence services are also stepping up their game. The FBI said it had identified a militant with a British accent seen executing Western hostages in IS videos.
In London, police arrested nine people suspected of links to radical extremism, including a notorious radical preacher.
The latest wave of strikes carried out overnight Wednesday to Thursday hit some of the small-scale crude refineries that IS gangs use to generate up to $2 million (1.6 million euros) in revenues per day.
The strikes by US and Arab warplanes against the oil refineries killed 14 jihadists but also left five civilians dead, including a child, according to the Britain-based monitoring group the Syrian Observatory For Human Rights.
The Pentagon said it was aware of reports of civilian casualties, and was investigating, but insisted raids are carried out with precision.
A spokesman said foreigners from Europe, Arab nations, Chechnya and Turkey made up the vast majority of the more than 140 jihadists killed since the US-led raids began in Syria earlier this week.
It said US planes also carried out fresh strikes against IS fighters in Iraq, destroying armed vehicles, a tank and other targets.
"The United States of America will work with a broad coalition to dismantle this network of death," Obama told the UN.
Also at the General Assembly, Iranian President Hassan Rouhani said the West was responsible for "strategic blunders" that had created terror havens, but also called for action against jihadists
'Determination and vigilance'
The IS group has committed widespread atrocities including mass executions of captured Iraqi soldiers, forced conversions of non-Muslims and the on-camera beheadings of Western hostages.
FBI chief James Comey said that the United States believed it had identified the masked IS militant who murdered the two American journalists, without naming the suspect.
It came a day after jihadists in Algeria posted video footage of the execution of an abducted Frenchman, Herve Gourdel, after Paris rejected their demand to halt strikes in Iraq.
President Francois Hollande pledged "determination, composure and vigilance" in the face of jihadi threats.
Muslim groups plan to hold a demonstration outside Paris's main mosque Friday to denounce the "barbarism" of Islamic State militants, as flags fly at half mast.
Underlining the global threat, the Philippines said it would not negotiate with a militant group threatening to behead one of two German hostages unless a huge ransom is paid and Berlin halts support for the campaign against IS.
In Iraq, jihadists were said to have executed a female rights activist who criticised IS on social media.
The US-led coalition has carried out some 20 strikes in Syria since the start of the week and Washington nearly 200 in Iraq since launching air raids there in early August.
The raids in Syria have hit IS positions, command centres, training compounds and vehicles, in their regional stronghold of Raqa and near the Syria-Iraq border.