ISTANBUL, Sept. 8 (Xinhua) -- Gursel Tekin, the court-appointed trustee for the main opposition Republican People's Party's (CHP) Istanbul provincial branch, assumed office on Monday under heavy police intervention, following a court ruling that annulled the party's provincial congress.

Since Sunday night, CHP lawmakers and supporters had staged a sit-in at the provincial headquarters, following a call from party leader Ozgur Ozel, to block Tekin, a former provincial chairman, from entering.

Tensions escalated when riot police used tear gas to disperse party members, including lawmakers, inside the headquarters, clearing the way for Tekin to take office.

Live footage aired by Halk TV showed many people affected by the gas. Suat Ozcagdas, a CHP lawmaker, told the broadcaster that police advanced through the building while firing tear gas.

A Turkish court on Sept. 2 annulled the party's Istanbul provincial congress held in 2023 and ousted Provincial Chairman Ozgur Celik and his administration over irregularities.

CHP's leadership said it did not recognize the court ruling, vowing to continue resisting the trustee appointment and denouncing all accusations.

Ozel called on citizens to gather at the headquarters to resist Tekin's entry. In response, police sealed off nearby roads and the Istanbul Governor's Office imposed a three-day ban on demonstrations in surrounding districts until Wednesday evening. ■