Islamic State reportedly has moved some of its high-ranking commanders and their families from its de facto capital of Raqqa to the nearby Syrian province of Deir Ezzor, activists and local groups said.
The move came as U.S.-backed forces continue their push toward Raqqa, where IS fighters have been in control since 2014.
Although the Kurdish-led Syrian Democratic Forces (SDF) this week succeeded in cutting off the main highway that links Raqqa to Deir Ezzor, local activists say that IS uses alternative routes that haven't yet been targeted by U.S.-led airstrikes and SDF fighters.
It is unclear how many IS commanders have moved to Deir Ezzor, but activist spokesman Hussam Eesa said that in recent days dozens of IS convoys have been observed heading toward the eastern city.
"There is at least one more route that [IS] uses to transport supplies and fighters between Raqqa and Deir Ezzor via the desert," said Eesa, of Raqqa Is Being Slaughtered Silently, an activist group that reports on IS activities in Raqqa and elsewhere.
Rami Abudlrahman, director of the Syrian Observatory for Human Rights, also confirmed to VOA that IS has transported some of its effective leaders and their families to the oil-rich Deir Ezzor.
Realizing the battle in the city of Raqqa is imminent, IS has begun looking for other options in hopes of keeping its caliphate alive, analysts said.
"Deir Ezzor is IS's next capital when Mosul and Raqqa are taken from it," said Nicholas A. Heras, a Middle East researcher at the Center for a New American Security, a Washington-based think tank.
While Syrian government troops control parts of Deir Ezzor city, much of the countryside is under IS rule. Strategic towns, such as Mayadeen and al-Boukamal, near the Iraqi border, have been IS strongholds since the inception of the terror group in 2014.
FILE - Islamic State runs this flour mill in a village near Deir Ezzor in eastern Syria, Oct. 18, 2016. (Credit: Dawa al-Haq)
"IS has been preparing Deir Ezzor to become its secret capital even before the battle to retake Mosul began in October 2016," said Mustafa Abdi, a media adviser with the Kurdish SDF. "This province represents an extension of IS's remaining reign in Iraq."
He told VOA that "when the Mosul offensive intensified, IS brought many leaders to both Raqqa and Deir Ezzor and so now some of those deployed to Raqqa have been moved to Deir Ezzor."
Deir Ezzor also has been home to IS's factories that make improvised explosive devices, activists said.
"When IS's factories in Iraq came under attack, they put more emphasis on their factories in Deir Ezzor," Abdi said.
IS commanders who recently have settled in Deir Ezzor, Abdi said, likely will direct operations against opposing forces in Raqqa and elsewhere, relying more on the explosive devices made in Deir Ezzor.
Meanwhile, airstrikes targeting IS's vital positions in Raqqa have intensified recently. Local reports said the number of civilian casualties also has increased.
At least seven civilians were killed and 17 others were wounded in an airstrike Wednesday that likely was carried out by the U.S.-led coalition, according to Smart News, a pro-Syrian opposition website.
Activists attributed that to a recent dress code imposed by IS on locals to confuse the coalition warplanes.
IS has "forced male residents of Raqqa to wear the Afghan clothes, an Islamic attire adopted by IS fighters," activist Eesa said.