Militants with the Islamic State group have plans to take Russian tourists hostage in Turkey and possibly smuggle them into Syria, Russia’s tourism agency warned Wednesday. The announcement comes as Russian tourism in Turkey has already dropped drastically since tensions between the two countries erupted in November last year, Agence France-Presse reported.

“We draw the attention of all independent tourists departing for Turkey to the necessity of taking all possible measures to ensure personal security,” the tourism agency said in a statement.

Turkey was the top travel destination for Russians last year, attracting some 3.2 million tourists. Its popularity sunk after the Turkish military shot down a Russian fighter jet over the Syrian-Turkey border in November. Russia responded by slapping on some sanctions and banning travel agencies from offering tours to Turkey.

The warning Wednesday was aimed at the remaining Russian tourists, who travel on their own in defiance of advisories against tourism to Turkey. Russian tourists have been threatened by ISIS militants in the past, as Moscow has been engaged in an airstrike campaign to bolster the embattled Syrian leader Bashar Assad.

In November last year, 224 tourists were killed on board a Russian airliner departing Sharm el-Sheikh, Egypt. An ISIS-affiliated group in Egypt’s Sinai region, called the Sinai Province, took responsibility for the attack. ISIS leaders said the attacks were in retribution for Russia’s airstrikes in Syria and were recorded handing out candy in an ISIS-held city in Syria, celebrating the deaths.

Fighting in Syria has spilled into Turkey in recent years, as some two millions Syrian refugees have settled in cities across the country. Turkey is a member of NATO and has been involved in the U.S.-led airstrike campaign against ISIS. Earlier this month, a suicide bomber who was believed to have supported ISIS targeted tourists in one of Istanbul’s most popular tourist district, killing 10 people.