The U.S. Embassy in Ankara said on Wednesday it had received reports that ¡°extremist groups¡± may be planning an attack against a Syrian opposition group in the southeastern Turkish city of Gaziantep.

It did not specify who might be targeting the Western-backed body, which sees itself as a government-in-exile but has little influence over rebels fighting to overthrow President Bashar Assad in a conflict that has been complicated by the successes of rival hard-line Islamist groups.

¡°The U.S. Embassy has received reports that extremist groups may be planning an attack against the Syrian Interim Government building,¡± the statement said.

¡°We remind U.S. citizens that the situation in southeast Turkey, while usually calm, can change without warning and U.S. citizens should avoid travelling in areas close to the Syrian border,¡± it said.

The body was formed by the Western-backed National Coalition for Syrian Revolutionary and Opposition Forces in November 2013. Early this year it set up its headquarters in Gaziantep, a province bordering Syria.

It exists to provide local services and support in rebel-held areas in Syria, but fighting, political squabbling and the reluctance of donors to support a partisan body have limited its influence.