Tanzania's police, accused by the opposition and rights groups of killing hundreds during recent election violence, issued a warning on Friday against further protests planned on December 9.

President Samia Suluhu Hassan was declared the winner of the October 29 poll with 98 percent of the vote, but it triggered widespread protests that were brutally suppressed by security forces.

Last week, Hassan announced a commission of inquiry into the killings, but the opposition said it was not "independent or impartial".

Activists and the opposition have called for a peaceful demonstration on December 9 to coincide with Tanzania's independence day.

But police said the plans "suggest a breach of the peace and promote hatred within the community, acts which are contrary to the law".

It warned officers "will not hesitate to take action against such matters, including statements using soft or harsh language intended to incite violence".

Any outbreak of violence would have "economic, social and security consequences" for all Tanzanians, it added.

Hassan's government has yet to provide any definitive figures for the number of people killed and injured during the election unrest.