US-backed fighters gained ground against the Islamic State group in the streets of Raqqa on Wednesday, a day after their months-long offensive finally broke into the jihadists' Syrian bastion.
The Syrian Democratic Forces militia has spent seven months advancing on the city, with backing from the US-led coalition bombing IS in Syria and neighboring Iraq.
Captured by the jihadists in 2014, Raqqa became synonymous with IS atrocities including beheadings and public displays of bodies, and also emerged as a hub for planning attacks abroad.
On Tuesday, the SDF's Arab and Kurdish fighters finally broke into the eastern Al-Meshleb district of the city.
Early on Wednesday, they captured the neighborhood and the Harqal citadel to the west of the city, the command of "Operation Wrath of the Euphrates" said.
The citadel sits on a hilltop roughly two kilometers (just over a mile) from the city limits.
Fighting was also raging in a military complex around two kilometers north of the city, the Syrian Observatory for Human Rights monitoring group said.
An activist with the Raqqa is Being Slaughtered Silently group said people in the city described non-stop bombardment.
"The bombing has been going for two days and hasn't stopped for more than an hour --it's air strikes, artillery fire and sometimes rockets," Abu Mohamed told AFP.
He said shops were barely open and that there were cuts in electricity and water supplies.
The Britain-based Observatory said the US-led coalition had carried out heavy bombing raids to back the advance.
One of Tuesday's air strikes inside the city killed eight civilians, including three children, Observatory head Rami Abdel Rahman told AFP.
160,000 inside Raqa
Reported civilian casualties in coalition air strikes have swelled as the SDF has ramped up its offensive.
Late on Monday, at least 21 civilians were killed in a coalition strike as they tried to escape Raqqa by dinghy on the Euphrates River, the Observatory said.
An estimated 300,000 civilians were believed to have been living under IS rule in Raqqa, including 80,000 displaced from other parts of Syria.
But thousands have fled in recent months, and the UN humanitarian office said on Tuesday that it estimated about 160,000 people remained in the city.
The International Rescue Committee said it was "deeply concerned for the safety of civilians in Raqqa" after a drop in numbers fleeing the city in the past week.
That decrease could indicate that IS intends to use remaining civilians "as human shields," the aid group warned.
The SDF has scored a series of victories since launching its operation to take Raqqa in November and on Tuesday announced the battle for Raqqa itself had begun.
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.
US-backed forces are battling IS in Mosul too and have now confined the jihadists to a few neighborhoods around the Old City.
Coalition commander Lieutenant General Steve Townsend said that defeating IS in Raqqa would "deliver a decisive blow to the idea of ISIS as a physical caliphate".
The coalition began striking IS jihadists in Iraq in August 2014 and expanded its operations to Syria the following month.
In recent weeks, it has also targeted pro-government forces near Syria's border with Jordan.
The coalition said on Tuesday that it had hit a regime convoy that was nearing the Al-Tanaf garrison, used by US and British troops to train Syrian rebels to fight IS.
The coalition said the contingent was "well advanced" into the 34-mile (55-kilometer) de-confliction zone, where any intrusion is considered hostile.
The Observatory said that at least 17 pro-regime troops were killed in the air strike.
It was the second time in less than a month that the coalition had attacked pro-regime forces near to the garrison, and government ally Russia slammed the strike as a "act of aggression."
Russian Foreign Minister Sergei Lavrov said the strikes "targeted those forces that are the most effective in fighting the terrorists on the ground."
Syria's foreign ministry in a statement Wednesday accused Washington of "leading a coalition that practices terrorism," and warned of "the dangers of escalation."
The Syrian army is eager to push east towards the Jordanian and Iraqi borders where some of the country's main oilfields lie before the area can be seized from IS by the SDF or Western-backed rebels.