AP have published a photo showing Turkish police securing an area of Istanbul's historic Sultanahmet district, a popular tourist area, following an explosion earlier this morning.
Harald Doornbos has linked to photos of the area in Istanbul where this morning's blast is thought to have taken place, based on media reports.
There are a number of reports emerging via social media of a gag order being imposed over the blast in Istanbul, but these are not confirmed.
Now Turkey's Hurriyet News is also reporting that a gag order has been imposed over reporting on this morning's blast in Istanbul, so that confirms the rumors.
It is not known who was behind the blast in Istanbul -- though there is plenty of speculation on social media, with some people saying that the IS group may be responsible.
The Istanbul governor's office said in a statement that "Investigations into the cause of the explosion, the type of explosion and perpetrator or perpetrators are underway."
The U.S. Embassy in Turkey has tweeted to say that it is closely following the reports of the explosion in Istanbul.
The explosion in Istanbul occurred at about 10:20 a.m. local time this morning in Sultanahmet Square in Istanbul near the Obelisk of Theodosius, Hurriyet reports.
The explosion was heard in many of Istanbul's districts.
So far, reports say that ten people have been killed and 15 more injured.
Another photo from Istanbul's Sultanahmet district, the site of this morning's explosion.
CNN Turk is still reporting on the explosion in Istanbul despite a media blackout.
According to CNN Turk, police are focussing on the possibility that a suicide bomber was responsible for the blast.
German and Norwegian tourists are among those killed in the blast this morning at Istanbul's main tourist district, Euronews is reporting, saying that the victims were part of a tour group.