Three orphans who are thought to be British have been found in a camp for people affiliated to Islamic State in an area of north-east Syria, which has come under attack by Turkish-backed forces.

Amira, 10, her sister, Hiba, eight, and their brother Hamza, who appeared to be about the same age as Hiba, are believed to have travelled to Syria with their parents from London five years ago. Their mother and father, an older brother and two other sisters were killed in an air assault on Isis-controlled Baghuz, which finally fell to Kurdish led-forces in March.

The children were discovered at the Ain Issa camp by a BBC reporting team, which broadcast an interview with Amira on Sunday in which she described being keen to get back to the UK. She said she and her surviving siblings have a grandmother, but she did not know her name. The children speak Arabic, but speak English when they are together and Amira has traces of a London accent. Hiba showed the camera a large scar on her abdomen, indicating the violence they appear to have endured.

Shortly after their whereabouts became known, the Britain-based Syrian Observatory for Human Rights said Turkish warplanes struck villages near the camp, 20 miles south of the Turkish-Syrian border, and hundreds of people in the secure camp escaped as clashes broke out between Turkey-backed Syrian fighters and Kurdish forces, local officials said.

The camp houses about 13,000 people, including nearly 1,000 foreign women with links to Isis and their children. According to the Kurdish-led administration in northern Syria, about 950 residents fled with Isis supporters attacking guards and storming the gates. Associated Press reported Jelal Ayaf, a senior official at the camp, as telling local media that 859 people escaped from the section housing foreigners. A few were recaptured but people from other sections of the camp also escaped and were carrying out attacks. The situation was “very volatile”, he said.

Turkey is fighting for control of an area of Kurdish-controlled northern Syria with the tacit backing of the US, which previously counted Kurds as allies but withdrew troops from the area early last week.

The chaos at the camp led to some US troops withdrawing from a base in Ain Issa because of the threat posed by Syrian fighters allied with Turkey. A US military official said the situation across north-east Syria was “deteriorating rapidly” and American forces were cut off from the Syrian Kurdish fighters.

Amira, whose surname is not known, told the BBC she left London at the age of five but recalled aspects of life in the UK, saying she would “go to a park, go to a funfair, go to a restaurant”.

Speaking in English, she then described the attack in which her parents and three siblings died.

“They were hitting so much,” she said. “There was a little house and that big dusty mountain and behind it everybody was dead. In front of us was everyone who was not killed, the other people.

“We were going to pack our stuff and get out, the airplane came and bombed. So then my mum died, my littlest brother, my little brother and my sister. Then after that, all was getting on fire. We had to walk out.”

Imagining her future life, she said: “When I grow up, I want to get fruits from the tree, I like to get waterlemon [sic], I like to get strawberries, I like to get cherries, I like to get blueberries, apples, oranges and bananas.”

A UK government spokesperson said: “There may be British children in internally displaced persons camps in Syria who, because of their age, are innocent victims of the conflict. We look at all evidence to determine someone’s nationality and will examine every single case where we are asked for consular assistance, but this process is far from straightforward.”