Jessica Durando, and Jim Michaels

USA TODAY

Three cities in separate countries hit by suspected Islamic State terrorists in the past week dealt a tumultuous blow to safety in those regions, heightening fears of the militants' capabilities and where they could strike next.

The reign of terror includes Sunday's massive suicide bombing in Baghdad that killed at least 157 people, the weekend hostage-taking at a restaurant in the Bangladesh capital of Dhaka that left 22 dead and Tuesday's bombing at the Istanbul airport that killed 44.

The massacres demonstrate that the Islamic State has established cells around the world — and is still capable of heinous attacks despite its recent setbacks on the battlefield.

"The Islamic State is losing territory in Iraq and Syria, but it is still a formidable opponent and very dangerous," Bruce Riedel, a former CIA officer and an analyst with the Brookings Institution, said Sunday.

The militant group claimed responsibility for the assaults in Baghdad and Dhaka, and is strongly suspected of being responsible for the Istanbul bombing.

Since the Islamic State has suffered losses over the past two years in more conventional military operations, the extremist group is now focusing on guerrilla warfare and terrorism, said Daniel Byman, a professor at Georgetown University's Walsh School of Foreign Service.

"We’ve already seen the number of foreign fighters going to Iraq and Syria decline. From the Islamic State’s point of view, these are desperate attacks. But they are successful in their own right and do indicate that we will see more attempts," said Byman, also a senior fellow at the Center for Middle East Policy at the Brookings Institution.

Islamic State exporting terror despite losses in Iraq

He added that the more desperate the Islamic State becomes, the more the group, also known as ISIL or ISIS, will rely on amateurs.

“ISIS has tens of thousands of individuals that are scattered not just in the Middle East but also to West Africa, to Southeast Asia, and beyond,” CIA Director John Brennan told the Council on Foreign Relations last week.

The Islamic State’s presence in other parts of Asia has also been growing in recent years, though its presence in the Middle East is larger. The Islamic State commands about 6,000 fighters in Libya.

Baghdad

Sunday's attack in Baghdad — one of the worst since the U.S. invasion in 2003 — reflects a shift in strategy for the Islamic State. As the militant group has been pushed out of territory it controls in Iraq and Syria, it has resorted to more conventional terror attacks against civilian targets.

The truck bombing comes one week after U.S.-backed Iraqi forces recaptured Fallujah, a city about 40 miles west of the capital, which was a major defeat for the terrorist organization.

The Iraqi government had hoped that driving the militants out of Fallujah would help prevent the Islamic State from getting bombs into Baghdad, since Fallujah straddles major roads into the capital. The U.S. air campaign had also expanded airstrikes to target car bomb factories used by militants in an effort to stop high-profile terror attacks, which pose a risk to the stability of the U.S.-backed Iraqi government.

Dhaka

A 10-hour siege ended Saturday at a restaurant in the heart of the capital city's diplomatic quarter with 20 hostages and two policemen dead. Hostages unable to quote from the Quran were pulled aside and hacked or knifed to death. Police killed six of the terrorists.

"In the case of ISIS and its connection to international terrorism in Bangladesh, they have mentioned the country several times in Dabiq, their online journal," Sajjan Gohel, the international security director at the Asia Pacific Foundation, told CNN. "They talked about the fact that they were going to carry out more attacks, they were going to increase the tempo, and they were calling for volunteers from Bangladesh to join them."

Bangladesh official doubts ISIL's claim for hostage-taking attack

The Islamic State has established a presence in Bangladesh, a predominately Muslim country, as it has in other parts of the world, said Patrick Johnston, a terrorism analyst at RAND Corp. The group has been able to build its presence in places like Bangladesh by exploiting local grievances and weak governments, Johnston said.

Istanbul

Three suspected Islamic State terrorists blew themselves up late Tuesday at Ataturk International Airport.

Residents said they were already bracing for something like this to happen again in Turkey, which has endured nearly 20 terrorist attacks that killed 300 people and injured more than 1,000 others in the past year.

"Almost every month since June 2015, there have been suicide bombings all over the country," said Ege Memis, 24, a student. "The only protection people have is their luck."

Istanbul too numb to be shocked by airport attack

The growing terrorist threat heightens the risk of destabilizing Turkey, a NATO member and U.S. ally in the war against the Islamic State.

“Turkey has been very vulnerable to terrorism,” said Bulent Aliriza, an analyst at the Center for Strategic and International Studies. “Turkey has been involved in balancing act for a year now. It is cooperating with the United States and trying to prevent ISIS from retaliating.”

Contributing: Victor Kotsev and Nikolia Apostolou