The United States has bombed militants near Baghdad in support of Iraqi forces, striking close to the capital for the first time in its expanded campaign against Islamic State jihadists.
But in a sign of their growing strength, a monitoring group said the jihadists had managed to bring down a Syrian warplane conducting strikes over their stronghold of Raqa in north-central Syria.
The US air strike against IS fighters in the Sadr al-Yusufiyah area, 25 kilometres (15 miles) from Baghdad, came as world diplomats pledged to support Iraq in its fight against the militants and less than a week after US President Barack Obama ordered a "relentless" war against IS.
"US military forces continued to attack (IS) terrorists in Iraq, employing attack and fighter aircraft to conduct two air strikes Sunday and Monday in support of Iraqi security forces near Sinjar and southwest of Baghdad," the US Central Command said in a statement.
"The air strike southwest of Baghdad was the first strike taken as part of our expanded efforts beyond protecting our own people and humanitarian missions to hit (IS) targets as Iraqi forces go on offence, as outlined in the president's speech last Wednesday."
The strikes destroyed six IS vehicles near Sinjar and an IS position southwest of Baghdad that had been firing on Iraqi forces.
- Purported photo of wreckage -
They bring the number of US air strikes across Iraq to 162.
Iraqi security spokesman Lieutenant General Qassem Atta on Tuesday welcomed the expanded American action, saying the US "carried out an important strike against an enemy target in Sadr al-Yusufiyah."
Sadr al-Yusufiyah lies in the Euphrates Valley, between the militant stronghold of Fallujah, west of Baghdad, and the key battleground of Jurf al-Sakhr, further south.
It is one of the closest front lines to Baghdad where Iraqi government forces and allied militia have struggled to defend their positions.
IS militants have seized a swathe of territory in Iraq and Syria, declaring an Islamic "caliphate", committing widespread atrocities and instituting a brutal interpretation of Islamic law.
As part of the extended campaign Washington has vowed to carry out strikes in Syria as well, despite warnings from President Bashar al-Assad's regime against violating its airspace.
On Tuesday, the jihadists shot down a Syrian warplane conducting strikes against them, the first time they have done so since the regime began bombing their stronghold of Raqa in July, the Syrian Observatory for Human Rights said.
"IS fighters fired on a military aircraft which crashed," the Britain-based monitoring group said.
"It is the first aircraft shot down since the regime launched air strikes against the jihadists in July following their declaration of a caliphate in late June," said the group, which relies on a wide network of doctors and activists for reports on the situation in Syria.
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A photograph posted on a jihadist Twitter account purported to show the wreckage of the plane.
"Allahu Akbar (God is greater), thanks to God we can confirm that a military aircraft has been shot down over Raqa," another account said, congratulating the "lions of the Islamic State".
The expansion of the US air campaign came as representatives from about 30 countries and international organisations, including the United States, Russia and China, vowed during talks in Paris on Monday to support Iraq in the fight against IS.
In a joint statement, diplomats promised to back Baghdad "by any means necessary, including appropriate military assistance, in line with the needs expressed by the Iraqi authorities, in accordance with international law and without jeopardising civilian security."
They stressed that IS militants are "a threat not only to Iraq but also to the entire international community" and underscored the "urgent need" to remove them from Iraq.
The Paris statement made no mention of Syria, but US Secretary of State John Kerry stressed again at the talks that "we're not going to coordinate with the Syrians."
A senior US official, speaking on condition of anonymity, warned that US forces will target Syrian anti-aircraft systems if they take aim at American planes conducting strikes inside Syria against IS.
- Target for major drive -
On the ground in Iraq, sporadic clashes broke out Monday near the town of Dhuluiyah, north of Baghdad, where security forces and allied tribesmen prepared for an operation against IS-led militants.
The area would appear to be the target of the next major drive against IS in Iraq, after a successful operation to break the siege of the town of Amerli farther north.
The Paris meeting was the latest in a series of frantic diplomatic efforts to build a broad global coalition against the jihadists, and German Foreign Minister Frank-Walter Steinmeier said meetings would come "thick and fast" ahead of a UN General Assembly next week.
Ten Arab states including Saudi Arabia are among the countries backing the US-led coalition, and Australia has pledged 600 troops.
"We are not building a military coalition for an invasion... but for a transformation as well as for the elimination of (IS)," Kerry told reporters.
"We are fighting an ideology, not a regime."
The beheading at the weekend of a British aid worker, the third Western hostage to be executed on camera, raised the stakes in the battle against the jihadists, who the CIA estimates have as many as 31,500 fighters.