BAGHDAD — A suicide bomber believed linked to the Islamic State in Syria set off a powerful blast Tuesday in one of Istanbul’s most popular tourist districts, officials said, killing at least 10 people and injuring 15 with reports citing Germans as among the main casualties.
The attack — in the shadow of the famous Blue Mosque — was a further sign of the country’s deepening instability in a region wracked by war and the expanding reach of groups such as the Islamic State, which uses Turkey as a critical lifeline for recruits, supplies and oil smuggling.
Turkey’s prime minister, Ahmet Davutoglu, described the bomber as a member of the Islamic State, but gave no other immediate details.
The blast also struck at the heart of Istanbul’s important tourism trade, reflecting similar tactics used by militants against internationally known sites in countries including Tunisia and Egypt.
Nine of those killed were Germans, the Associated Press reported, citing sources in the Turkish prime minister’s office. The other victim was a Peruvian man, Peru’s foreign ministry said.
In addition, at least 15 people were injured in the explosion, including nine Germans and other foreigners, officials said.
Turkish officials also have blamed the Islamic State for recent bombings elsewhere in Turkey. At the same time, Kurdish separatists and domestic left-wing groups have carried out other attacks in the country.
“I strongly condemn the terror incident that occurred in Istanbul . . . an attack by a Syria-rooted suicide bomber,” said Turkish President Recep Tayyip Erdogan.
Turkey’s deputy prime minister, Numan Kurtulmuş, told reporters that the attacker was identified as a 28-year-old Syrian. Turkish media outlets later identified the bomber as Nabil Fadli, who was born in Saudi Arabia.
It was unclear if Fadli was a dual Syrian-Saudi citizen, or if he was born in Saudi Arabia to a Syrian family.
The blast occurred just before 10:30 a.m. in the Sultanahmet district, an area that includes the 400-year-old Blue Mosque and Hagia Sophia complex, a former Byzantine-era basilica.
The vast plazas and surrounding streets are normally busy with merchants, vendors and visitors, including many part of tour groups. The blast was centered near a local tram station close to the Obelisk of Theodosius, an ancient Egyptian monolith brought to Istanbul — then known as Constantinople — in the 4th century.
In Berlin, German Chancellor Angela Merkel said at least nine Germans were injured in the blast. The Dogan agency also reported that Norwegians and a Peruvian were among those hurt.
“Today Istanbul was hit. Paris has been hit. Tunisia has been hit. Ankara has been hit before,” Merkel said in Berlin. “International terrorism is once again showing its cruel and inhuman face today.”
The attack in Istanbul comes as Turkey is grappling with instability from the five-year-old crisis in neighboring Syria. Turkish forces have not directly intervened in the Syrian conflict but have been under Western pressure to crack down on the cross-border flow of people and supplies to Islamic State strongholds in Syria.
Turkey is also a main backer of rebel groups opposing Syrian President Bashar al-Assad, and it has recently stepped up its decades-old fight against Kurdish separatists. Other Turkish political cells have staged their own attacks.
“If today’s attack was perpetrated by the Islamic State, it would reflect a shift in the group’s strategy and herald a broader campaign against Turkey,” said Firas Abi Ali, senior analyst at IHS Country Risk, a global risk analysis firm.
But such a move “will likely provoke a significant backlash by the Turkish government,” Ali said.
A year ago, a Chechen woman believed linked to militant factions blew herself up outside a police post in Sultanahmet. One police officer also was killed.
There were two major suicide bomb attacks on peace activists in the country’s southeast last year, killing more than 100 people. The government blamed the Islamic State for those explosions, but the militant group never asserted responsibility.
Just before New Year’s, Turkish officials said they foiled a plot to launch a wave of attacks over the holiday.
Turkey last summer opened its Incirlik air base to U.S. warplanes carrying out airstrikes against Islamic State positions in Syria.
“Given that the Islamic State has established a significant logistics and support base network in Turkey — used to smuggle people and supplies into its territories — the Islamic State most likely has the capability to launch an extended terrorist campaign inside Turkey,” said Ali, the security analyst.
The group’s latest videos, in which its fighters threaten Turkey, “suggest that it calculates that a confrontation with Turkey is inevitable,” he added.
Tourism directly contributes more than $30 billion to Turkey’s gross domestic product each year, according to government records. That is nearly 4 percent of the GDP overall, but Turkey’s tourism is heavily concentrated in locations such as Istanbul and the country’s Aegean and Mediterranean coasts.
Nearly 40 million people visited Turkey in 2014, the Ministry of Tourism and Culture said.
“By striking in the heart of Istanbul’s old city, which has many mosques, museums, and tourists . . . ISIS is also targeting Turkey’s lucrative tourism industry,” said Soner Cagaptay, an expert in Turkish politics at the Washington Institute for Near East Policy. ISIS is one of the acronyms for the Islamic State.
Murphy reported from Washington.