At least 31 people were killed and more than 100 others wounded in protests that erupted across Kenya on Monday, a rights group said, as simmering anger against President William Ruto’s government boiled over into clashes between protesters and the police.

The group, the Kenya National Commission on Human Rights, said on Tuesday that it had also documented at least 532 arrests and two forced disappearances.

The police fired live rounds, rubber bullets, tear gas and water cannons at protesters across the country, the group said. From atop deserted overpasses across Nairobi, the capital, officers blasted tear gas canisters at demonstrators congregating below. Some protesters threw rocks at the police, while others danced.

The demonstrations on Monday occurred on Saba Saba Day, which commemorates the start of Kenya’s multiparty democracy movement in 1990. Saba Saba, which in Swahili means “Seven Seven,” refers to the first pro-democracy rallies held in Nairobi.

In a major show of force, armed police officers barricaded and blocked major roads leading to Nairobi’s central business district, leaving normally crowded streets deserted save for a few determined protesters who traveled on foot.