Less than a week after an attack in Istanbul, five people have been arrested in Bulgaria.

They are accused of "assisting the probable perpetrator of the act of terrorism" with six dead, as the spokeswoman for the Bulgarian Attorney General, Sijka Milewa, told state radio in Sofia on Saturday.

With the arrests in the EU state of Bulgaria - a country neighboring Turkey - the number of those arrested in connection with the Istanbul attack rose to 22, including the main suspects.

On November 13, six people were killed and more than 80 injured in an attack on a busy Istanbul shopping street.

Turkey blames the Syrian Kurdish militia YPG and the banned Kurdish Workers' Party PKK.

Both groups have denied this.

According to the Turkish police, the main suspect is a Syrian citizen.

The spokeswoman explained that those arrested in Bulgaria provided “rather logistical and communication assistance” after the attack.

She gave no details - such as the nationality of those arrested or how they got to Bulgaria.