Two Pakistani-origin sisters from London are believed to be the latest set of mothers to lose their British citizenship for marrying into the Islamic State (ISIS) terrorist group in Syria.

Reema Iqbal and her sister, Zara, have five boys under the age of eight between them and are being held in a Syrian detention camp.

Reports of them losing their right to return to the UK after losing their citizenship rights come as it was confirmed that Bangladeshi-origin Shamima Begum lost her three-week-old baby in a Syrian refugee camp days after her British citizenship was similarly revoked.

The Sunday Times quoted legal sources to say that the Iqbal sisters, from east London, have had their British nationality rights revoked for marrying into an ISIS terrorist cell.

Their parents are from Pakistan, so the UK Home Office would argue they are eligible for Pakistani nationality instead. Their five sons, however, are likely to remain British citizens.

The newspaper report says the two women headed to Syria from London in 2013 after marrying into a six-man cell of ISIS recruits with close links to the filmed murders of western hostages by British Arab ISIS fighter Mohammed Emwazi, dubbed Jihadi John for his UK connection. The sisters’ husbands were later killed in fighting.

Zara, 28, already had a son when she made the journey and was heavily pregnant with her second child, to whom she gave birth in Syria. She later had a third boy under the so-called ISIS caliphate .

The family is believed to be in either Al Hol camp or another facility at Ain Issa in Syria.

Her older sister, Reema, 30, has two sons, one of whom was born in Britain. They are in Roj camp, to which Shamima Begum was reportedly recently transferred.

There is growing pressure on UK home secretary Sajid Javid since it was confirmed that 19-year-old Begum had lost her child, Jarrah, to pneumonia in the refugee camp on Thursday.

Diane Abbott, the UK shadow home secretary, said the baby’s death was a stain on the conscience of this government .

Javid’s own Conservative Party colleague and former justice minister, Phillip Lee, urged the government to “reflect” on its “moral responsibility” for the tragedy.

“We cannot just export the problem, he said.

A UK government spokesperson said: “The death of any child is tragic and deeply distressing for the family.”

The UK Home Office said it did not comment on individual cases, adding that decisions to withdraw citizenship from individuals were evidence-based and not taken lightly .

Under international law, the UK can revoke a citizenship of a British national only if the individual would not be made stateless and can acquire the citizenship of another country.

The use of the powers has risen sharply in the UK, with 104 deprivations of citizenship in 2017, compared to 50 in the previous decade, according to Home Office figures obtained by the immigration law website Free Movement.

At least a dozen jihadi brides from Britain and more than 20 of their children are believed to be held in overcrowded camps run by western-backed Kurdish forces in Syria.