ISTANBUL (AFP) - The Turkish authorities have detained one person over the suicide attack in Istanbul that killed 10 mainly German tourists, Interior Minister Efkan Ala said on Wednesday.
"One person was detained in operations carried out yesterday (Tuesday) evening. The investigation is continuing in a very intensive way," he told a news conference alongside German Interior Minister Thomas de Maiziere, without explaining the suspect's role in the strike.
Mr Maiziere said there is no indication that the suicide attack specifically targeted Germans, adding there was no need for nationals to cancel travel plans.
"In the current stage of the investigation, there is no indication that the attack was targeted against Germans. I see no reason to refrain from trips to Turkey," Mr de Maiziere told the news conference.
"It was an attack against humanity," he added.
Ankara has said that Tuesday's attack was carried out by a 28-year-old Syrian who belonged to the Islamic State in Iraq and Syria (ISIS) group and had recently entered Turkey from Syria.
In the wake of the attack, Turkish security forces rounded up 68 suspected ISIS members across the country, state media said, but it was not clear if any of them were directly connected to the Istanbul bombing.
"The investigation is continuing in a very intensive way," Mr Ala told the news conference.
The German Foreign Ministry has advised its nationals to keep away from large groups in public places and tourist attractions in Istanbul.
German tourism giant TUI said customers who had booked trips to Istanbul can switch destination without paying a penalty.
Turkey has been hit by a string of deadly attacks blamed on militants over the last year, including a double suicide bombing in October in Ankara that killed more than 100 people.
But Tuesday's bombing was the first time in recent memory tourists had been targeted in the heart of Istanbul.
The bomber, identified as Nabil Fadli, detonated his charge on Sultanahmet Square which is home to Turkey's most visited historic sites including the Ottoman-era Blue Mosque and Hagia Sophia church.
The explosion went off by the Obelisk of Theodosius, a monument from ancient Egypt that was re-erected by the Roman Emperor Theodosius and is one of the city's most iconic landmarks. The Sabah daily said the bomber had entered Turkey as a refugee from Syria on January 5.
He was then fingerprinted by the Turkish migration service, explaining why the authorities were able to identify the bomber so rapidly after the attack.
The Hurriyet daily said Turkey's spy agency had twice issued warnings over the risk of a suicide attack in Istanbul.
Police on Wednesday removed a cordon preventing access to the area of the attack, which was quickly thronged by media and some tourists, an AFP correspondent said.
Some placed red roses by the obelisk, which appeared to have sustained no damage in the bombing.
Almost all of the victims were German, with Ankara giving the figure of nine while Berlin put the number at eight.
Peru also said one of its nationals had died in the attack.
Another 15 people were wounded, most of them Germans but also Norwegians, Peruvians and at least one Turk.
Two Germans were in serious condition.
The tourists were part of a group of 33 who had been staying at a boutique hotel in the upmarket Galata district and had been bussed to Sultanahmet that morning, media reports said.
"I saw the young man pull the pin and I shouted 'run!' in German. Then we started to run away, and the bomb instantly exploded," the group's tour guide Sibel Satiroglu told investigators, the Hurriyet newspaper said.
In impromptu remarks at his weekly audience, Pope Francis called on all believers to pray for the victims.
"May the Lord, the merciful, bring eternal piece to the departed, comfort to their families, the solidarity of all society and may he convert the hearts of violent men," he said.
Long accused of failing to crack down on ISIS, Turkey has in recent months moved against militant cells operating on its territory.
Among those arrested in the wake of Tuesday's bloodshed were 16 people suspected of planning a major attack in Ankara, Anatolia news agency said.
On Wednesday, three more suspected ISIS members were detained in the southern resort city of Antalya. All three are Russian citizens, it added.
And a week before the attack, 220 people "identified" as ISIS members were detained in Turkey, the interior minister said on Wednesday.
Despite criticism from Western allies that it was not doing enough in the fight against ISIS, Turkey is now hosting aircraft from the US-led coalition engaged in deadly attacks on the militant group's strongholds.