An opposition party says its Istanbul chief has been sentenced to nine years in jail for crimes including insulting Turkey president Recep Tayyip Erdoğan.

Canan Kaftancioglu, who heads up the Republican People's Party (CHP) in the city, was handed a sentence of nine years.

The indictment against Kaftancioglu cited several tweets she shared between 2012 and 2017.

She was convicted for several crimes that include insulting the president and spreading terrorist propaganda.

It comes just months after CHP fought a bitter battle with Erdogan's AK Party (AKP) over the mayoralty of Istanbul.

AKP's candidate narrowly lost the race to be Istanbul's mayor following elections in March before the electoral board annulled the result.

CHP's Ekrem İmamoğlu then won the re-run, this time by a wider margin, 54% to 45%.