Police in Myanmar repeatedly used tear gas and rubber bullets Tuesday against crowds protesting last month’s coup, but the demonstrators regrouped after each volley and tried to defend themselves with barricades as standoffs between protesters and security forces intensified.

Myanmar authorities have escalated their crackdown on the protests in recent days, making mass arrests and firing into the crowds. The United Nations said it believed at least 18 people were killed on Sunday by security forces. Foreign ministers from Southeast Asian countries were meeting Tuesday to discuss the increasingly volatile crisis.

Despite the crackdown, demonstrators have continued to flood the streets — and are beginning to more rigorously resist attempts to disperse them. Hundreds, many wearing construction helmets and carrying makeshift shields, gathered in Myanmar’s largest city of Yangon, where a day earlier police had fired repeated rounds of tear gas. They dragged bamboo poles and debris to form barricades, chanted slogans and sang songs at the police lines. They even threw banana skins onto the road in front of them in a bid to slow any police rush.

The mainly young demonstrators fled in panic each time tear gas canisters were fired but soon returned to their barricades. Videos posted on social media showed similar chaotic scenes in the Insein neighborhood of northern Yangon.

Protesters also took up their flags and banners to march through the streets of Dawei, a small city in southeastern Myanmar that has seen almost daily large demonstrations against the coup. One group of demonstrators was targeted by the security forces as it entered a narrow street on its way to pay respects at the house of a man killed in Sunday’s crackdown. Another was attacked on the main street in the city’s center.

Police also dispersed protests in Mandalay, the country’s second-largest city, on Tuesday.

Yangon, Dawei and Mandalay were among the cities where security forces reportedly fired live ammunition into crowds Sunday, according to the Unite Nations Human Rights Office. There were reports that they also fired live rounds Tuesday, but they could not immediately be confirmed.

Some fear the junta’s escalating use of force is meant to provoke a violent backlash by the demonstrators — who have largely remained nonviolent — in order to discredit them and justify an even harsher crackdown. Videos from recent days show a greater number of protesters trying to stand their ground and throw objects at the police.