What happened on Tuesday?
A suicide bombing took place in Sultanahmet Square, a popular tourist area in Istanbul. The incident is expected to have a negative impact on tourism in the country.
The bombing killed ten people, all German, and injured 17 others. Of the 11 people who were hospitalised, nine were German, one was Norwegian and one Peruvian.
"We will continue our fight against terrorism with the same resolve, and will never take a step back," Turkish Prime Minister Ahmet Davutoglu was quoted as saying during a meeting at the Cankaya Palace in Turkey's capital Ankara.
What have the Turkish authorities said about the bombing?
At a press conference with his German counterpart Thomas de Maiziere on Wednesday, Turkish interior minister Efkan Ala said that an "investigation is continuing in a very intensive way." Ala announced on Thursday that seven people were detained for connection to the attacks.
The Turkish government said earlier that a 28-year-old Syrian—who is a member of ISIS—is responsible for the attack and entered Turkey from Syria as a refugee, a result that that quickly reached. Davutoglu said the skull, face and nails of the Saudi-born Nabil Fadli confirmed that he was the suicide bomber.
"If you consider the way the attack happened and the general trend of it, we have identified Islamic State as the primary focus," Reuters quoted Davutoglu as saying to Turkey's NTV television. "It was definitely a suicide bombing...DNA tests are being conducted. It was determined how the suicide bombers got there. We're close to a name, which points to one group."
Did ISIS claim its responsibility for the attack?
ISIS haven't claimed responsibility which is unusual; ISIS and the groups linked to it in the Middle East usually move quickly to declare responsibility for the operations they execute.
The nature of the relationship between Turkey and ISIS is somewhat opaque. Last October, Turkish investigators accused of ISIS of two suicide bombings that targeted a protest in the capital Ankara, leading to the death of 100 people and injury of more than 200 others.
Demonstrators were calling for an end to the renewed confrontations between government troops and the Kurdistan Workers' Party (PKK). Some of Erdogan's opponents had accused him of having a greater interest in fighting the PKK than ISIS.
Turkey, a NATO member-state, signed an agreement with the United States in February last year on training and equipping more than 400 Syrian opposition fighters who will fight ISIS.
The NATO partners reached further understandings in July. Turkey accepted allowing US planes to launch air strikes against IS militants from the US Incirlik air base near the Turkish-Syrian border. Later, both sides agreed to create an "ISIS-free zone" in northern Syria along the borders with Turkey by pushing IS militants away from a 60-mile strip, although this has not been carried out yet.
The agreement aimed to eventually bring the area under the rule of pro-western Syrian rebels, which would then allow for a return of Syrian refugees into a safe territory. After the October attacks, Erdogan vowed to "act militarily" against ISIS. He said in November that 2,000 militants "inside and outside the country" were killed. Also dozens of suspected militants were arrested.
The Istanbul attacks came one month after Russia said it had proofs that Erdogan and his family were involved in oil-smuggling activities from ISIS-controlled areas in Syria and Iraq. In a press conference, Russian officials presented satellite pictures of tanker trucks loading from ISIS-controlled oil facilities and transferring them to Turkey.
In the meantime, Davutoglu announced on Thursday that the Turkish military has attacked 500 ISIS positions in Syria and Iraq, killing 200 militants.
What was the response of the German government?
German Chancellor Angela Merkel, who had phone conversations with both President Recep Tayyip Erdogan and Davutoglu, expressed solidarity with the families of the victims, saying "we stand by your side" and offering condolences to Turkish citizens.
"We feel a sense of solidarity with Turkey," she said, adding that those who carry out such attacks, be it in Paris, or Copenhagen or Istanbul, have the same target -- "our free life and free society."
"The terrorists are the enemies of all free people, they are enemies of humanity, be it in Syria, Turkey or France or Germany," she said, stressing that Berlin would fight such terror "with determination."
German Interior Minister Thomas de Maiziere pointed out that there is "no indication" that the bombing was targeting German people in specific, asserting no willingness to stop the travelling of Germans to Turkey. Yet, the German foreign ministry called on Germans to stay away from "large groups" in public and tourist sites in Istanbul.