Political manipulation of Congo's security forces has brought crackdowns on opposition parties and may lead to bloodshed in this month's election, the United Nations said in a report on Wednesday.

New York based-Human Rights Watch said the U.N. report documented just a fraction of the actual abuses. The European Union and African Union issued separate warnings of a deteriorating political situation in the central African country.

Congo is due to hold presidential and parliamentary elections on November 28, but preparations are far behind schedule, the early stages of campaigning have been increasingly violent and there are fears of results being challenged in unrest.

President Joseph Kabila is seen as favourite against a divided opposition, but his challengers have strong support among the country's many ethnic communities.

The report, produced by the U.N.'s Joint Human Rights Office, documented 188 cases of election-related violence between November 2010 and September 2011.

The report notes worrying trends of manipulation of the state's police, intelligence and justice sectors by political actors, it said in its introduction.

The report added: A trend seems to be emerging wherein parties are targeted more often in regions where they have significant numbers of followers and are predicted to be the biggest threat against the ruling majority and the President.

Etienne Tshisekedi, one of Kabila's main rivals, has a strong following in the teeming capital, Kinshasa, as well as the southern Kasai provinces. Vital Kamerhe, a former ally of the president's, is popular in the east of the country.

The U.N. said at least four people have been killed during political demonstrations so far.

Continued repression and rights abuses may increase the likelihood of individuals and political parties resorting to violent means, endanger the democratic process and lead to post-electoral violence, the U.N. report said.

Congo's head of police was not immediately available for comment. Lambert Mende, Congo's minister of communications, said he was not aware of a report but such charges were politicised.

It is totally unfair to our police, they are suffering, they are doing their job. We shall succeed in these elections and Congo will be for the Congolese, he added.

Post-war elections in 2006 were widely backed by the U.N. and other donors. This time Kinshasa is taking the lead in running the poll itself.

CLIMATE OF FEAR

The 2006 vote was followed by several bouts of urban gun battles between Kabila's forces and those loyal to former rebel Jean-Pierre Bemba, who was defeated in a run-off vote.

This time, analysts say the threat of violence is more likely to stem from street protests.

The U.N. report was released as the world body's peacekeeping mission said it was deeply concerned by the rising spate of pre-electoral violence across the country.

The EU's election observer team also issued a statement criticised the muzzling of pro-opposition media, and warned politicians against inciting violence.

For its part, the AU called for restraint and condemned statements by Tshisekedi earlier this week, in which he declared himself already president.

A law banning insults against the head of state has been used to prosecute people who criticised Kabila, and police agents have beaten, threatened and arrested civilians just for wearing opposition T-shirts, the U.N. report said.

It said an opposition supporter has been in detention since March 18 for possessing a journal questioning Kabila's nationality. The east, which voted heavily for Kabila in 2006, was of particular concern, it added.

Ida Sawyer, Congo researcher for Human Rights Watch, said aggression by the security forces has created a climate of fear and risks undermining the credibility of the elections.