British police say they have received a report that two missing 17-year-old boys are in Syria.

West Yorkshire police said Tuesday the boys had disappeared from their homes last week.

Police say they are believed to have taken a flight from Manchester airport to Turkey on March 31.

Counter-terrorism police say a report indicates the boys then traveled on to Syria, where the Islamic State group is fighting the government and other rebel factions.

Assistant Chief Constable Mark Milsom said the boys' families are "gravely worried" and that the top police priority is to bring the boys home safely.

A growing number of young people have tried to travel from Britain to Syria to join extremists there.