Police in Myanmar's biggest city fired tear gas Monday at defiant crowds who returned to the streets to protest last month's coup, despite reports that security forces had killed at least 18 people a day earlier. The protesters in Yangon were chased as they tried to gather at their usual meeting spot at the Hledan Center intersection. Demonstrators scattered to rinse the irritating gas from their eyes, but later regrouped. The coup reversed years of slow progress toward democracy in Myanmar after five decades of military rule. It came February 1, the same day a newly elected Parliament was supposed to take office. Ousted leader Aung San Suu Kyi's party would have led that government, but instead she was detained along with President Win Myint and other senior officials. The army has leveled several charges against Suu Kyi — an apparent effort by the military to provide a legal veneer for her detention and potentially to bar her from running in the election the junta has promised to hold in one year. On Monday, Suu Kyi made a court appearance via video conference and was charged with two more offenses, her lawyer Khin Maung Zaw told reporters. Accused of inciting unrest, she was charged under a law that dates from British colonial days and has long been criticized as a vaguely defined catch-all statute that inhibits freedom of expression. That charge carries a maximum sentence of two years in prison. The other charge from Monday carries a one-year sentence. Following her detention on the day of the coup, the 75-year-old Suu Kyi was initially held at her residence in the capital of Naypyidaw, but members of her National League for Democracy party now say they don't know where she is. Since the takeover, a movement of protests in cities across the country has been growing — and the junta's response has become increasingly violent. The U.N. said it had "credible information" that at least 18 people were killed and 30 were wounded across Myanmar on Sunday. Counts from other sources, such the Democratic Voice of Burma, an independent television and online news outlet, put the death toll in the 20s. Any of the reports would make it the highest single-day death toll since the military takeover. The junta has also made mass arrests, and the independent Assistance Association for Political Prisoners reported that as many as 1,000 people were detained Sunday. Several journalists have been among those detained. At least five people are believed to have been killed Sunday in Yangon when police shot at protesters, who have remained nonviolent despite provocation from the security forces and pro-military counter-demonstrators. In Dawei, a small city in southeastern Myanmar where five people were reported killed Sunday, the number of protesters on the streets was lower than usual, but they paraded to the applause of bystanders. Confirming the deaths of protesters has been difficult in areas outside Yangon, Mandalay and Naypyidaw. But in many cases, there was evidence posted online such as videos of shootings, photos of bullet casings collected afterwards and gruesome pictures of bodies.