How far does ISIS' global reach extend?

Their bloodthirsty advances have sent hundreds of thousands of refugees streaming across the borders into neighboring countries, like Turkey, increasing the risks of instability there.

But the recent expansion of U.S. airstrikes against ISIS into Syria, as well as a call by a leader of the extremist group for attacks against Western citizens, has raised questions about how far the militants' reach extends beyond the Middle East.

With anti-terrorist raids in Australia, the beheading of a French citizen in Algeria and reports of ISIS sympathizers in Indonesia, here's a look at the countries that could be affected.

The United States

No sign of attacks being planned

U.S. officials have repeatedly said that they have no information to suggest that ISIS is planning an attack on the U.S. homeland at the moment.

But the group recently called on devotees around the world to carry out attacks against people in the United States and other Western countries.

After the U.S. and Arab partners began airstrikes against ISIS targets in Syria this week, the U.S. Department of Homeland Security issued a bulletin warning law enforcement agencies to be on heightened alert for "lone-wolf" terrorist attacks on U.S. soil, a U.S. law enforcement official told CNN.

Officials said that law enforcement agencies receive similar bulletins on a fairly regular basis as a precaution.

'Al Qaeda's playbook'

Security analysts say the calls for lone-wolf attacks in the United States are nothing new.

"It's taking a page out of al Qaeda's playbook," said Robert McFadden, a senior vice president at the Soufan Group, a security consultancy.

The United States has in recent years experienced homegrown attacks that were apparently motivated by extremist Islamic views, including the Boston Marathon bombings and the Fort Hood shootings.

But many lone-wolf attacks in the U.S. in recent decades were committed by people not linked to any terrorist organization, like Timothy McVeigh, who bombed the federal building in Oklahoma City in 1995, and more recently, Aaron Alexis, who carried out the deadly shooting at the Navy Yard in Washington last year.

Guarding against individuals acting on their own is extremely difficult, experts say, as there are no orders coming down through organizations.

"Almost all the time it's not there," McFadden told CNN. "So that ingredient makes it so much more tough to combat these kind of things and root that out."

Other group targeted

U.S. authorities are also trying to monitor the more than 100 American citizens who have traveled to Syria to fight for armed groups there, including ISIS.

The Americans who have come to harm at the hands of ISIS are James Foley and Steven Sotloff, journalists who were abducted in Syria and beheaded by the militant group in recent weeks.

While U.S. officials say they have no knowledge of any planned attacks by ISIS in the United States, they have suggested that Khorasan, a separate terrorist group that was also hit in the airstrikes on Syria, was actively plotting against U.S. and other Western targets.

Australia

Anti-terrorism raids

Earlier this month, Australian police carried out large-scale raids after investigations suggested suspects were planning "a random attack on individuals."