(CNN) -- The United Nations Security Council has condemned political violence in Guinea that reportedly killed nearly 160 people.
Police arrest a protester on Monday near a stadium in Guinea's capital Conakry during a protest.
The council Wednesday expressed its "utmost concern" about reports that government troops fired on people attending a political rally and that rapes occurred "on public streets" in broad daylight, said Susan Rice, the U.S. ambassador to the United Nations.
The council urged authorities in Guinea to end the violence, bring to justice those responsible, release political prisoners and allow a return to democratic rule with elections scheduled to be held next year, Rice said.
Violence erupted Monday in the West African nation at a stadium full of people attending a political rally.
Western governments and human rights groups say the Guinean military opened fire on civilians.
The Guinean government has said most of the victims were crushed as the crowd stormed the stadium doors. "According to preliminary investigations, most of the innocent victims died as a result of being crushed in the crowd," a statement on the government's Web site said.
Reports put the death toll at 157, with more than 1,200 people injured, U.S. State Department Spokesman Ian Kelly said in a statement Tuesday.
"The United States condemns the Guinean military's brazen and inappropriate use of force against civilians," Kelly said. "The military also stands accused of carrying out brutal rapes and sexual assaults on women demonstrators and bystanders during its rampage."
On Tuesday, the African Union expressed its "grave concern" about the situation. "The (AU) Commission strongly condemns the indiscriminate firing on unarmed civilians, which left dozens dead and many others injured, while serious other violations of human rights were committed," the AU stated.
Tens of thousands of people were protesting the rule of Capt. Moussa Dadis Camara, who seized power in a bloodless coup in December, according to U.S.-based Human Rights Watch.
The United States demanded the immediate release of opposition leaders and a return to civilian rule, the State Department statement said.
Human Rights Watch also condemned the violence against "generally peaceful demonstrators" and urged the government "to hold accountable the security forces." It quoted victims and witnesses who said security forces sexually assaulted women at the demonstration and also attacked demonstrators with knives and bayonets.
"Women were raped by soldiers in the stadium. I saw them," former Guinean prime minister Sidya Touré told the French newspaper Le Monde. Touré led the country from 1996-1999 and was participating in the peaceful demonstration.
Christine Jamet, of Doctors Without Borders, was in Conakry and said that her organization saw victims both with injuries resulting from being crushed, and others with gunshot wounds.
The people who came seeking aid were in shock over the incident, Jamet told CNN.
The government blamed "certain political leaders" for staging the demonstration despite being asked not to do so and warned that security could not be guaranteed for the gathering.
The leaders stormed the stadium, "breaking down doors and the main entryways, causing much violence that left dozens of victims, including 53 who died by suffocation and four killed by ricocheting bullets, which were recorded that day by authorities working with the Guinean Red Cross and verified by hospital officials," the government said.
It accused the leaders of looting two police commissaries before the demonstrations, letting prisoners out of jail and stealing weapons.
The government said it condemns "these deliberate acts in violation of the law, and are working to find and bring to justice those responsible for these reprehensible acts."
The capital was mostly quiet after the incident, Jamet said, but later in the day people started opening up shops and resuming their regular activities.
The AU noted that the violence comes amid serious uncertainties and setbacks in the effort to restore constitutional order to Guinea after the December coup. The AU urged the coup leaders to stick to their vow not to run for office in the January presidential election.
The European Union's foreign policy chief Javier Solana, also condemned the actions of security forces in Conakry on Monday.
Solana called "for the immediate release of the arrested political leaders and call(ed) on the authorities to exercise maximum restraint and ensure a peaceful and democratic transition."
Guinea was thrown into turmoil in December after the death of President Lansana Conte. He was one of only two presidents to rule Guinea, after it gained independence from France in 1958.
Conte came to power in 1984, when the military seized control of the government after the death of the first president, Sekou Touré.
Following his death, Camara seized control in a bloodless military coup and declared himself president of the National Council for Democracy, which he called a transitional body that would oversee the country's return to democracy.