Russian units have begun patrolling territory separating Turkish-backed Syrian rebels from the Syrian army around the flashpoint town of Manbij in north-east Syria, in a clear sign that Moscow has become the de facto power broker in the region after the evacuation of US troops.

Oleg Blokhin, a Russian journalist usually attached to mercenaries in Syria, posted a video on social media on Tuesday from a deserted US military base in the village of al-Saadiya, near Manbij.

“They [the US] were here yesterday, we are here today,” he said. “Now we’ll see how they were living and what they were doing.”

MrRevinsky (@Kyruer) #Syria #EasternEuphrates#Russia|n PMC inside the #US base in #Manbij abandoned this morning. pic.twitter.com/II2FI68aBx

Meanwhile, the flag of the Syrian regime was raised above Manbij for the first time in years, Syrian state media reported, after Kurdish officials agreed a deal allowing their former opponents to protect both the contested town and nearby Kobane from a six-day-old Turkish assault.

Regime troops entered Manbij on Monday night and, at the same time, Syrian rebel proxies loyal to Turkey massed to the west ahead of a planned attack.

Quick guide What is happening in north-eastern Syria? Show Hide Who is in control in north-eastern Syria? Until Turkey launched its offensive there on 9 October, the region was controlled by the Syrian Democratic Forces (SDF), which comprises militia groups representing a range of ethnicities, though its backbone is Kurdish. Since the Turkish incursion, the SDF has lost much of its territory and appears to be losing its grip on key cities. On 13 October, Kurdish leaders agreed to allow Syrian regime forces to enter some cities to protect them from being captured by Turkey and its allies. The deal effectively hands over control of huge swathes of the region to Damascus. That leaves north-eastern Syria divided between Syrian regime forces, Syrian opposition militia and their Turkish allies, and areas still held by the SDF – for now. On 17 October Turkish president, Recep Tayyip Erdoğan, agreed with US vice-president Mike Pence, to suspend Ankara’s operation for five days in order to allow Kurdish troops to withdraw. The following week, on 22 October, Erdoğan and his Russian counterpart, Vladimir Putin agreed on the parameters of the proposed Turkish “safe zone” in Syria. How did the SDF come to control the region? Before the SDF was formed in 2015, the Kurds had created their own militias who mobilised during the Syrian civil war to defend Kurdish cities and villages and carve out what they hoped would eventually at least become a semi-autonomous province. In late 2014, the Kurds were struggling to fend off an Islamic State siege of Kobane, a major city under their control. With US support, including arms and airstrikes, the Kurds managed to beat back Isis and went on to win a string of victories against the radical militant group. Along the way the fighters absorbed non-Kurdish groups, changed their name to the SDF and grew to include 60,000 soldiers. Why does Turkey oppose the Kurds? For years, Turkey has watched the growing ties between the US and SDF with alarm. Significant numbers of the Kurds in the SDF were also members of the People’s Protection Units (YPG), an offshoot of the Kurdistan Workers’ party (PKK) that has fought an insurgency against the Turkish state for more than 35 years in which as many as 40,000 people have died. The PKK initially called for independence and now demands greater autonomy for Kurds inside Turkey. Turkey claims the PKK has continued to wage war on the Turkish state, even as it has assisted in the fight against Isis. The PKK is listed as a terrorist group by Turkey, the US, the UK, Nato and others and this has proved awkward for the US and its allies, who have chosen to downplay the SDF’s links to the PKK, preferring to focus on their shared objective of defeating Isis. What are Turkey’s objectives on its southern border? Turkey aims firstly to push the SDF away from its border, creating a 20-mile (32km) buffer zone that would have been jointly patrolled by Turkish and US troops until Trump’s recent announcement that American soldiers would withdraw from the region. Erdoğan has also said he would seek to relocate more than 1 million Syrian refugees in this “safe zone”, both removing them from his country (where their presence has started to create a backlash) and complicating the demographic mix in what he fears could become an autonomous Kurdish state on his border. How would a Turkish incursion impact on Isis? Nearly 11,000 Isis fighters, including almost 2,000 foreigners, and tens of thousands of their wives and children, are being held in detention camps and hastily fortified prisons across north-eastern Syria. SDF leaders have warned they cannot guarantee the security of these prisoners if they are forced to redeploy their forces to the frontlines of a war against Turkey. They also fear Isis could use the chaos of war to mount attacks to free their fighters or reclaim territory.

On 11 October, it was reported that at least five detained Isis fighters had escaped a prison in the region. Two days later, 750 foreign women affiliated to Isis and their children managed to break out of a secure annex in the Ain Issa camp for displaced people, according to SDF officials. It is unclear which detention sites the SDF still controls and the status of the prisoners inside. Michael Safi

The strategically located town of Manbij, a US base for three years, remains a major military target for Turkey, its president, Recep Tayyip Erdoğan, said on Tuesday. Shelling between Turkish proxy Syrian rebel forces and Kurdish-led Syrian Democratic Forces (SDF) positions continued at intervals throughout the day, although there have been no reports yet of fighting inside the city itself.

Moscow’s special envoy to Syria, Alexander Lavrentyev, said on Tuesday Russia opposed the Turkish operation and would not allow direct clashes between Nato member Turkey’s troops and Syrian forces. The two sides stopped short of a direct confrontation when Ankara first put boots on the ground in Syria in 2016 to seize the area around Jarablus from Isis, in the process hampering the expansion of the SDF.

“[Fighting between Turkey and Syria] would simply be unacceptable … And therefore we will not allow it, of course,” Lavrentyev said during a visit to the United Arab Emirates, adding that Turkey and the regime were in direct contact – a major reversal since the early years of Syria’s war, in which Ankara backed calls for the removal of Syria’s president, Bashar al-Assad.

Erdoğan spoke to the Russian president, Vladimir Putin, on Tuesday about the need to prevent armed clashes between Turkish and Syrian regime troops. According to the Kremlin, Putin invited the Turkish leader for a working visit to Moscow “in the coming days” and Erdoğan accepted.

As Putin exercised his enhanced influence in Syria, Washington was scrambling to limit the damage of Donald Trump’s acquiescence in the Turkish offensive. After announcing sanctions that critics described as ineffective, Trump dispatched key figures to Ankara including his vice president, Mike Pence, the secretary of state, Mike Pompeo, national security adviser, Robert O’Brien, and special envoy on Syria, James Jeffrey.

A White House statement said Pence would “reiterate President Trump’s commitment to maintain punishing economic sanctions on Turkey until a resolution is reached.”

Erdoğan has so far refused to ease military operations, boasting on Tuesday that his troops had seized 1,000 sq km (400 sq miles) of territory from the SDF, an alliance that Ankara has long maintained is an offshoot of the militant Kurdistan Workers’ party (PKK).

The SDF was America’s ground partner in the five-year campaign against Isis and lost 11,000 troops in the long battle. Trump has attempted to rebut accusations even from his most loyal supporters that the move amounted to a betrayal.

Despite the prospect of losing the area’s semi-autonomous status, Kurdish officials struck a Russian-brokered deal with Damascus on Sunday for reinforcements to protect Kurdish-held border positions. There are unconfirmed reports that talks are still under way to implement a Russian-enforced no-fly zone over the area.

Syrian state media showed residents cheering the arrival of troops loyal to Assad in Manbij and Ain Issa, waving flags and throwing rice before the path of soldiers. The regime flag was also briefly raised above the famous clocktower square in Islamic State’s former capital of Raqqa on Monday night, a source in the city said, before it was taken down again by the SDF.

Heavy fighting in the border towns of Tel Abyad and Ras al-Ayn as well as airstrikes and shelling of other Kurdish-controlled roads and towns has displaced 160,000 people from their homes and killed at least 165 civilians. SDF counterattacks over the border have left 20 Turkish civilians dead, including a Syrian baby.

Erdoğan said that despite the threat of US and EU sanctions, as well as European arms embargos, Ankara would press on with the creation of a proposed 20-mile-deep (32km) “safe zone” on its border stretching from Manbij to Iraq, in which Turkey wants to resettle up to 2 million Syrian refugees. Turkey denies the resettlement of mainly Arab Syrians from other parts of the country would amount to demographic engineering.

The offensive has been widely condemned for precipitating a humanitarian crisis and risking the return of Isis, after about 750 people with links to the militant group took advantage of the chaos on Sunday to escape from a Kurdish-run detention camp. Footage of Syrian rebel proxies summarily executing nine Kurdish civilians on a major highway have also prompted allegations of war crimes.