Two explosions shook a crowded Nairobi park during a rally late Sunday, killing at least five people and wounding at least 70 more, authorities said. Voice of America (VOA) reported that the bombs went off while the rally attendees were saying prayers at the conclusion of the gathering called in by opposition of the country's proposed new constitution that is up for a vote in August. A man who said he was at the park told VOA he heard two separate explosions. "There was an explosion from the left side," the unidentified man said. "We thought maybe it was just a truck or just a tire. Then we saw some people injured, and there was a bomb there. After another 2 minutes, another explosion kicked off." VOA said witnesses and Kenyan television said the blasts were caused by gasoline bombs. Kenya's Daily Nation newspaper said it wasn't clear what caused the explosions. Prime Minister Raila Odinga condemned the attack and Kenyan Internal Security Minister George Saitoti appealed for calm. "I would like to ask for patience while the government is carrying out a full investigation to be able to determine the manner in which these crimes were committed and who was behind it," Saitoti said.