KUWAIT CITY (AP) — Authorities in Kuwait are warning they will use harsher measures to crack down on anti-government demonstrators defying bans on protest gatherings in the increasingly tense Gulf nation.

Thursday’s statement followed clashes between security forces and thousands of protesters demanding the release of an opposition leader, Musallam al-Barrack, who is under investigation for allegedly insulting Kuwait’s emir.

Kuwait last week banned any public gathering of more than 20 people in attempts to quash growing protests led by opposition factions that include Islamists. The opposition is seeking to reclaim control of parliament in elections planned for Dec. 1.

Kuwait’s Interior Ministry said forces will “firmly” confront any new protests.

It says a “number” of protesters have been arrested, including a driver who allegedly tried to run over four policemen late Wednesday.