The area is home to the the world-famous monuments including the Blue Mosque and Hagia Sophia.
Ambulances and police were immediately dispatched to the area.
[PHOTOS]: Ten killed, 15 wounded in Istanbul blast
An explosion of unknown origin rocked the historic centre of Istanbul on Tuesday.
Here is what we know so far (Malaysian time):
10.33pm: At least nine Germans were among the 10 people killed in the suicide bombing, a Turkish government official said.
"There are at leat nine Germans among the 10 killed," the official told AFP after the suicide bombing ripped through the historic Sultanahmet district.
5.39pm: The governor's office confirmed that ten people were killed and 15 wounded.
"Investigations into the cause of the explosion, the type of explosion and perpetrator or perpetrators are underway," it said in a statement quoted by the Dogan news agency.
5.17pm: Based on witnesses account, AFP reported the blast was sufficient to be heard in adjacent neighbourhoods. TV reports said several were wounded but there was no further detail on the toll.
In October last year, at least 86 people were killed in the Turkish capital Ankara when twin blasts ripped through groups of leftist and pro-Kurdish activists gathering for an anti-government peace rally.
READ: Turkey says two male suicide bombers behind Ankara blasts
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READ: Malaysia strongly condemns bomb attack in Ankara - Najib
READ: No Malaysian victims in Ankara bombings - Foreign Ministry
