HARARE, Zimbabwe (AP) — Zimbabwean police have increased threats against civic groups a week away from a referendum on a new constitution and before crucial elections to end the nation’s shaky coalition later in the year, rights organizations said Saturday.

An alliance of 15 human rights, pro-democracy and labor groups said police mounted “a sustained and escalating assault” on activists to discredit their organizations ahead of polling. The state Electoral Commission announced Friday that groups under police investigation or leaders facing any charges will not be allowed to observe the referendum vote on March 16.