HARARE, Zimbabwe — 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. At least four main groups, including the independent Zimbabwe Election Support Network, have had police raids on their offices this year. The alliance said its member groups have reported growing political tensions across the country, even though the referendum vote is not being contested. All the main political parties have called for a ‘Yes' vote from their supporters. Most civic groups are facing “vague and generalized search warrants, arrests, persecution and prosecution,” said the alliance. Police on Friday said they will charge Jestina Mukoko, head of the Zimbabwe Peace Project, a group that monitors political intimidation and violence, for running an organization not legally registered as a private voluntary body. They also allege she smuggled into Zimbabwe cheap radio receivers capable of tuning in to stations other than those of the state broadcasting monopoly controlled by loyalists of President Robert Mugabe and mobile phones with the Global Positioning System (GPS) for “suspicious and unauthorized use” during elections across the country. Lawyers acting for her group deny any of its activities were illegal and say it is properly registered under a deed of trust with the Zimbabwe High Court, like most other human rights groups in the country. As well as Mukuko's group, the Zimbabwe Human Rights Association, the election support network and another smaller organization in the second city of Bulawayo have been raided by police who seized documents, voter education materials and the solar-powered and hand cranked radio receivers destined for impoverished communities without traditional sources of information surrounding elections. The alliance of rights groups said Saturday the continuing threats by police commanders who have openly voiced their allegiance to Mugabe were intended to portray civic groups as unpatriotic and serving the interests of Mugabe's opponents and their alleged Western backers and funders in Britain, and the United States.— AP