The Foreign Office is investigating reports that two Britons have died fighting in Syria.
The pair are believed to have been fighting for the Islamic State in Iraq and the Levant (ISIS), an Islamist group linked to al-Qaeda.
A Foreign Office spokesman said: "We are aware of reports and are looking into them."
More top news
An attacker armed with a machete killed a woman and wounded two others in the southern German city of Reutlingen.