An international coalition pounded Raqa with air strikes Thursday, with a monitor saying at least 17 civilians had been killed in the bombardment as US-backed fighters pushed further into the Islamic State group's Syrian bastion.
The Syrian Observatory for Human Rights said US-led coalition forces had hit the city and its suburbs with at least 25 strikes, warning that dozens had been injured and the death toll could rise.
One of the strikes hit an internet cafe in the western suburb of Jazra where most of the dead were found, said Rami Abdel Rahman, head of the Britain-based monitor.
The air strikes came after US-backed fighters with the Syrian Democratic Forces (SDF) battled deeper into Raqa, two days after finally entering following a months-long struggle to surround a city that has become synonymous with IS atrocities since its capture by the jihadists in 2014.
On Wednesday, an AFP journalist entered the city with SDF fighters and witnessed heavy clashes in the Al-Meshleb neighbourhood, with IS firing mortar rounds towards the advancing forces.
The SDF did not allow journalists to return to the city on Thursday where fighting was continuing.
"Our troops are advancing in Al-Meshleb and control parts of it," said SDF spokesman Talal Sello.
"The international coalition forces are working with us on the ground in the battle for Raqa in a highly effective manner," he told AFP.
On Wednesday, the US-led coalition said it had carried out 22 strikes near Raqa, hitting IS fighting positions and vehicles as well as a weapons cache and a training camp.
The Observatory said the SDF now controlled around two-thirds of Al-Meshleb and was some 400 metres (yards) from the neighbouring Al-Senaa district.
"IS has snipers monitoring Al-Meshleb neighbourhood and has laid mines extensively throughout it," the monitor said.
US special forces
Fighting was also continuing on the western outskirts of the city, it added, saying US special forces were actively participating in battles on several fronts.
On Wednesday, an AFP correspondent saw coalition armoured vehicles parked among olive trees in the desert east of Raqa, covered with camouflage fabric.
Pentagon spokesman Eric Pahon said "hundreds" of US military personnel were taking part in the Raqa offensive. It was unclear how many were US special forces, and Pahon said the role of such troops remained unchanged.
"They are still advising and assisting" the SDF, he said, saying US troops were accompanying SDF units moving into the city but "the SDF have the lead in the fight".
Pahon said up to 2,500 IS fighters were still holed up in Raqa.
SDF male and female commanders, dressed in fatigues and sporting colourful printed scarves wrapped around their heads, pored over maps on tablet devices to pinpoint targets.
Raqa has become infamous for IS atrocities including beheadings and public displays of dead bodies, and also emerged as a hub for planning attacks abroad.
An estimated 300,000 civilians were believed to have been living under IS rule in Raqa, including 80,000 displaced from other parts of Syria.
But thousands have fled in recent months, and the UN humanitarian office estimates about 160,000 people remain in the city.
Raqa is Being slaughtered Silently -- an anti-IS group -- has said conditions in the city are deteriorating, describing continuous bombardment and water and electricity outages.
Civilians who have escaped have described harrowing journeys and being targeted by IS as they fled.
The International Rescue Committee said this week it was "deeply concerned for the safety of civilians in Raqa," noting a drop in the numbers leaving the city.
That decrease could indicate IS intends to use remaining civilians "as human shields," the aid group said.
Civilians trapped in Raqa also face the risk of heavy coalition air strikes.
The number of reported civilian casualties in the coalition's strikes has swelled as the SDF offensive has intensified.
Along with Mosul in Iraq, Raqa was one of the twin pivots of the self-styled Islamic "caliphate" that IS declared nearly three years ago.
Iraqi forces backed by the coalition are also battling IS in Mosul, where the jihadists are now confined to a few neighbourhoods.
The Syrian military has so far been absent from the battle for Raqa, though state news agency SANA said Thursday that the air force had targeted IS positions in the west of Raqa province.
The Observatory said these strikes were carried out by Syria's ally Russia.
Elsewhere on Thursday, US forces shot down a pro-regime drone in southern Syria after it fired at US-led coalition forces, said coalition spokesman Ryan Dillon.
No one was hurt in the incident, which occurred near the coalition's At-Tanaf garrison.
"It was armed and still had weapons on it when it was fired upon by US forces from an aircraft," Dillon said.
Around 300,000 civilians were believed to have been living under IS rule in Raqa, infamous for IS atrocities||US-backed fighters pushed further into the Islamic State group's Syrian bastion