The Russian foreign ministry said the 32 toddlers had been held in Iraqi jails. The mothers are either serving out sentences or awaiting trial for membership of the Islamic State group (IS).

The health ministry said the children, who arrived in Moscow late Monday, were taken straight to a hospital for medical tests.

Monday's group were among 122 minors, aged between one and 15 years, sent from Iraq to Russia since December last year, the authorities said, adding that the last such repatriation was in July.

Russian nationals were among the largest contingents of IS fighters. Most of the "returnees" were women and children and are in Muslim-majority regions of the Caucasus, notably Chechnya.

Countries such as Britain and France have withdrawn the citizenship of Islamist fighters, while the Russian authorities, notably Chechen President Ramzan Kadyrov, have encouraged their return.

But in early November, the head of the Russian intelligence agency FSB, Alexander Bortnikov, warned of the risks of the possible return of some 2,000 wives and children of Islamists who fought in Iraq and Syria.