WASHINGTON: Nearly 30,000 people, including more than 250 Americans, have left their countries to join militants fighting in Syria and Iraq, many with the Daesh group, according to a report released on Tuesday.

The study said the US government lacks a strategy for combating such travel, and called for measures including better information sharing, within the US and internationally.

Thirty thousand doubles the total estimated number of such fighters a year ago, when authorities also said about 100 Americans had joined, or tried to join the fighting in Syria and Iraq.