°®Âþµº

on Thursday upheld a prison sentence for the Istanbul leader of the country's main opposition, the party told AFP, in a crackdown on government critics ahead of 2023's presidential polls.

In 2019, , 50, of the secular Republican People's Party (CHP), had been sentenced to nearly 10 years in jail on a range of charges including "terrorist propaganda" and insulting President Recep Tayyip Erdogan.

The charges related mostly to tweets Kaftancioglu posted between 2012 and 2017. She had been free pending the appeals.

The Supreme Court of Appeals on Thursday approved her conviction on three counts with a prison term of four years, 11 months and 20 days.

It was not immediately clear if the ruling means will be jailed right away.

The CHP is the second largest party in the Turkish parliament after Erdogan's Islamic-rooted AKP party, holding 135 seats.

'Canan is not alone'

called on his lawmakers to head to the party's Istanbul headquarters.

"All lawmakers of our party, immediately set off for our Istanbul provincial headquarters," he tweeted right after the ruling.

Dozens of supporters flooded the party centre in Istanbul to welcome Kaftancioglu, who travelled from the capital Ankara, according to AFP journalists on the ground.

"Chairwoman Canan is not alone," the crowds shouted. "The pressure cannot deter us".

Kaftancioglu, a doctor by profession, played a key role in the shock victory of the CHP's mayoral candidate Ekrem Imamoglu in 2019- the first time Erdogan's party had lost power in Turkey's biggest city for 25 years.

Kaftancioglu "is my comrade with whom we are striding together to change Istanbul," Imamoglu tweeted.

"I find this decision political and condemn it. I stand by our chairwoman".

'Revenge'

Rights groups regularly accuse of using the judiciary as a political tool, particularly after thousands of judges were purged in the wake of an attempted coup in 2016.

Erdogan railed against Kaftancioglu after she was appointed to the Istanbul chair in 2016.

CHP lawmaker Engin Ozkoc chastised Erdogan for exerting "huge pressure on the opposition" one year ahead of the election.

"The judiciary in Turkey acts not according to law but according to Tayyip Erdogan," he argued.

The Turkish leader has seen his once overwhelming support shrink in the past year amid the weakening lira and nearly .

"Erdogan doubles down on suppression as (he) loses ground amid growing economic pressure in the country," Seren Selvin Korkmaz of Istanbul-based think tank IstanPol Institute commented.

"Kaftancioglu is a rising figure within the CHP and frequent government target. The (ruling AKP party) tries to take revenge of losing Istanbul by sending her to prison".

vowed not to give in.

"We will never stop, never give up, never get tired," she tweeted in a video message.

"Wherever we are, we will send the evil in power,Ìýand breathe all together when we establish the rule of law".

Among the tweets used by the prosecution against Kaftancioglu was one in which she criticised the death of a 14-year-old boy hit by a tear gas grenade during the mass "Gezi Park" protests of 2013.

The latest ruling comes on the heels of a life sentence handed by an Istanbul court to another Erdogan critic and activist, , last month.

A leading figure in Turkey's civil society, the 64-year-old Kavala was accused of attempting to topple Erdogan's government by financing the 2013 protests.