Abidjan, Ivory Coast (CNN) -- Violence in Ivory Coast was ongoing amid a tense political standoff Wednesday, after at least five police officers were killed and three U.N. peacekeepers were wounded in an Abidjan neighborhood, and three other police officers were killed in clashes with protesters, officials said.
The five police officers were killed Tuesday night by heavily armed gunmen in what authorities said was a targeted attack in the densely populated Abobo area of the city, a police source said Wednesday.
The three U.N. peacekeepers sustained minor injuries overnight when they "came under crossfire from both sides of the road" while returning from a patrol, the U.N. operation in Ivory Coast said in a statement Wednesday. The U.N. forces -- a joint team of military and U.N. police -- were forced to return fire, the operation said.
Five other people were killed earlier Tuesday in clashes between police and supporters of the nation's president-elect amid an ongoing political standoff in the West African nation, an official said.
The dead included three police officers and two demonstrators, the governor of Abidjan said Tuesday. The deaths came a day after the U.N. Security Council condemned the violence that has erupted since the country's November 28 presidential runoff election and "urged all parties to exercise restraint."
The incidents came a day after forces belonging to self-declared President Laurent Gbagbo blocked and looted a food convoy, the operation said, adding it "reiterates its call for calm and urges all parties concerned to avoid recourse to violence."
Amnesty International issued a statement warning of a fresh outbreak of violence in the wake of the five officers' deaths, which it said happened early Wednesday.
"Some of the worst armed clashes so far broke out in the city of Abidjan today," the organization said. An unidentified witness told Amnesty International of having heard "heavy exchanges of fire" around midnight and seeing Wednesday morning "three military vehicles burnt out" and the body of a member of the security forces, the statement said.
State-run RTI reported the government has imposed a curfew on the Abobo and Ayaman neighborhoods of Abidjan, where the violence occurred. The curfew is in place from Wednesday until 6 a.m. Saturday, it said.
The cocoa-producing nation was plunged into crisis when Alassane Ouattara was declared the winner of the election, but the incumbent, Gbagbo, refused to leave office.
The Security Council expressed its support for efforts by the African Union and the Economic Community of West African States in pursuing a peaceful resolution of the crisis.
At the same time, the council repeated its readiness to impose measures -- including sanctions -- against those who threaten the peace process by blocking the work of the U.N. mission and others or "commit serious violations of human rights and international humanitarian law."
Meanwhile, Ouattara is willing to add Gbagbo supporters to his Cabinet, provided the incumbent steps down, Ivory Coast's ambassador to the United Nations said this week.
Ambassador Youssoufou Bamba said Ouattara would not enter a power-sharing government similar to that in Zimbabwe but that he would be open to a unity Cabinet.
U.N. spokesman Farhan Haq could not confirm any such offer from the Ouattara government and said that U.N. Secretary-General Ban Ki-moon still calls for Gbagbo to step down in an orderly transition.
Ouattara told CNN last week that he welcomes a proposal for direct negotiations with Gbagbo -- on the condition that Gbagbo recognize Ouattara as president.
But in a telephone interview Tuesday, Gbagbo spokesman Ahoua Don Melo rejected the idea, saying Ouattara "should first go to the Constitutional Council to get recognized as the president before making any proposal."
An independent election commission declared Ouattara the winner of the vote, but the country's Constitutional Council invalidated those results and declared Gbagbo the winner.
The U.S. Treasury froze Gbagbo's assets in the United States last week and barred Americans from doing business with him. His wife and three top aides also were sanctioned.
Ouattara remains in the Golf Hotel under the protection of U.N. peacekeepers.
The United Nations and an ever-increasing number of other nations have recognized Ouattara, a former prime minister, as the rightful election winner.
The United States and other countries have offered Gbagbo what they call a "dignified exit," which could mean living and working in other countries, including the United States.
Gbagbo, however, has ignored those offers and has refused to accept telephone calls from U.S. officials.
Ouattara has said he will ensure protection for Gbagbo if he concedes, said Kenyan Prime Minister Raila Odinga, the African Union envoy for a multinational mediation effort.
U.N. Security Council members have also "strongly condemned and demanded an immediate halt" to media efforts to "propagate false information to incite hatred and violence," and condemned the ongoing blockade around the Golf Hotel.
Meanwhile, the United Nations' refugee agency is building a refugee camp for Ivorians fleeing to neighboring Liberia. The camp will initially be capable of housing some 18,000 refugees, it said.
At present, there are about 25,000 Ivorian refugees in Liberia, with about 600 more arriving daily, it said.
The Office of the U.N. High Commissioner for Refugees said it has sufficient relief supplies for about 30,000 people in Liberia and "is ready to mobilize stocks from Ghana for an additional 30,000 people if the need arises."
CNN's Whitney Hurst and Journalist Eric Agnero in Abidjan contributed to this report.