A suicide bomber killed 10 people, at least nine of them German tourists, in Istanbul's historic heart. The bomber was a 28-year-old Syrian national, Deputy Prime Minister Numan Kurtulmus said. Turkish Prime Minister Ahmet Davutoglu claimed the perpetrator was a member of Islamic State (Isis) and pledged to battle IS (Daesh) until it no longer "remains a threat" to Turkey or the world.

The blast occurred in the Sultanahmet district, Istanbul's main sightseeing area, home to the Topkapi Palace and the former Byzantine church of Hagia Sophia, now a museum. The explosion, which could be heard in districts of Istanbul several kilometres away, was at a park that is home to a landmark obelisk, near the historic Blue Mosque.

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Turkish police secure the area after an explosion in Istanbul's popular Sultanahmet districtCan Erok/Getty Images
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Emergency services attend the scene after an explosion near the Ottoman-era Sultanahmet mosque, known as the Blue mosque in Istanbul, TurkeyOsman Orsal/ Reuters
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A body is seen on the ground as police secure the area after an explosion in Istanbul's Sultanahmet districtCan Erok/Getty Images

Several bodies lay on the ground in Sultanahmet square, also known as the Hippodrome of Constantinople, in the immediate aftermath. It was not densely packed at the time of the explosion, according to a police officer working there, but small groups of tourists had been wandering around. Tourist sites including the Hagia Sophia and nearby Basilica Cistern were closed on the governor's orders.

Norway's foreign ministry said one Norwegian man was injured and was being treated in hospital. The Dogan news agency said nine Germans and one Peruvian were also wounded.

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A food vendor stands in a deserted square in front of the New Mosque, following an explosion in IstanbulMurad Sezer/Reuters
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The Arasta Bazaar near the Blue Mosque is empty following an explosionMurad Sezer/Reuters
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A woman takes photographs in front of the New Mosque by the Bosphorus strait in IstanbulMurad Sezer/Reuters
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People react after a blast in Istanbul's Sultanahmet tourist hubSean Gallup/Getty Images
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Tourists take pictures outside the Blue Mosque after a blast in Istanbul's tourist hub of SultanahmetBulent Kilic/AFP
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A sign announces that a shop is closed after a blast in the Sultanahmet areaBulent Kilic/AFP

German Chancellor Angela Merkel decried the attack. "Today Istanbul was hit; Paris has been hit, Tunisia has been hit, Ankara has been hit before," she said. "International terrorism is once again showing its cruel and inhuman face today."

Germany and Denmark have warned their citizens to avoid crowds outside tourist attractions in Istanbul.

More Germans visit Turkey than any other nationality. More than 15% of all visitors to the country during the first nine months of 2015 were German. Tourism in Turkey has grown 200% in the past decade, according to the Turkish Investment Support and Promotion Agency.

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The Sultanahmet Mosque (also known as the Blue Mosque) is seen in front of the Hagia SophiaiStock
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Two young Muslim boys wearing regal outfits for their circumcision ceremony walk with family members through the main inner courtyard of the Blue Mosque on 29 March 2015Sean Gallup/Getty Images
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Tourists photograph the interior of the Sultanahmet Mosque (also known as the Blue Mosque)Sean Gallup/Getty Images
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Visitors walk through the main entrance gate at Topkapi PalaceSean Gallup/Getty Images
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A visitor tours the private apartments of the Ottoman Sultan at Topkapi PalaceSean Gallup/Getty Images
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Visitors snap a selfie while touring the private apartments of the Ottoman Sultan at Topkapi PalaceSean Gallup/Getty Images
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Tourists shop at the spice market, also known as the Egyptian Bazaar, in IstanbulMurad Sezer/Reuters
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Spices are displayed for sale at an outdoor market in IstanbulSean Gallup/Getty Images
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Fish are displayed for sale at a market under Istanbul's Galata BridgeOsman Orsal/Reuters
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People stroll along Istiklal street as a tram rattles bySean Gallup/Getty Images
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Visitors stroll through Beyoglu district next to Galata TowerSean Gallup/Getty Images
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The Bosphorus bridge is pictured through the window of a passenger aircraft flying over IstanbulMurad Sezer/Reuters
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Tourists look at the old city from the historical Galata Tower, with the Hagia Sophia museum and Blue Mosque in the backgroundMurad Sezer/Reuters
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People eat next to ornate boats selling grilled fish on the Golden Horn near Galata BridgeSean Gallup/Getty Images
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Huseyin Erdogan poses for a photo at his shop selling traditional ceramics in Istanbul's Grand Bazaar, the world's most visited tourist attractionChris McGrath/Getty Images

The attack raised fears of further damage to Turkey's vital tourism industry, already hit by a diplomatic row with Moscow, which has seen Russian tour operators cancel trips after the downing of a jet.

However, not everyone is worried about the effect on tourism. Kursat Yilmaz, who has operated tours for 25 years from an office near Sultanahmet square, said he had sold a package to a tourist from Colombia just an hour after the blast. "The reality is the world has grown accustomed to terrorism. It's unfortunate, and I wish it weren't true, but terrorism now happens everywhere: Paris, Germany, California and people are used to it," he said. "The agenda changes quickly in this age. If tourism is affected, it will be temporary. These things pass but the Hagia Sophia and the Sultanahmet mosque are eternal."