MINSK, Belarus — A homemade bomb exploded at an outdoor concert in the capital of Belarus early Friday and wounded at least 50 people, government officials said, blaming hooligans.

The bomb exploded in downtown Minsk at a concert marking the ex-Soviet nation's independence day.

Minsk police spokesman Alexander Lastovsky said more than 20 people were hospitalized, but the Health Ministry put that number at more than 50. The bomb was rigged with nuts and bolts.

Belarusian Interior Minister Vladimir Naumov said that police later found an unexploded homemade bomb in the same area. The cardboard juice carton contained explosives along with nuts and bolts, a device similar to the one that exploded.

"It had many fingerprints and other traces that could allow us to solve the crime," Naumov told reporters.

Lastovsky, the police spokesman, said it was "an action by hooligans."

Belarusian Emergency Situations Ministry spokesman Alexei Usatov said the bomb went off about 12:30 a.m. The concert was held at the Hero City memorial, which commemorates Minsk's suffering during World War II.

Dmitry Kudyakov, a 32-year-old engineer at the concert, said he felt a strong shock wave and saw smoke.

"People started crying," he said. "Some fell on me and there was a lot of blood."

Viktor Sirenko, chief doctor of the city's Emergency Hospital, said that three people were in grave condition. "We are struggling to save their lives," he said.

Viktor Gurko, chief doctor of the city Hospital No. 6 displayed nuts and bolts and doctors recovered from the victims' bodies.

Most of those injured were people in their 20s, but two children aged 5 and 6 and several elderly people also were among the victims.

Belarus a country of 10 millionm has been tightly controlled by authoritarian President Alexander Lukashenko.

Lukashenko, who was attending the concert, inspected the explosion site and urged officials to quickly track down the perpetrators.