Demonstrators marched in Myanmar on Monday in defiance of a crackdown by security forces that killed more than 18 people a day earlier, as calls grew for a more united international response after the worst violence since a coup one month ago.

Clashes occurred in many parts of the country on Sunday and police opened fire on crowds in the biggest city of Yangon, after tear gas and warning shots failed to clear protesters demanding the restoration of Aung San Suu Kyi’s cabinet.

Police with water cannon and military vehicles were mobilized at protest hotspots in Yangon on Monday, while protesters marched in Kale, in northwest Myanmar, carrying pictures of Suu Kyi and chanting “democracy, our cause, our cause”.

Live video on Facebook showed a small crowd in hard hats gathered across a street in Lashio, Shan State, chanting slogans as police marched towards them.

“It has been 1 month since the coup. They cracked down on us with shootings yesterday. We will come out today again,” protest leader Ei Thinzar Maung posted on Facebook.

The country has been in chaos since the army seized power and arrested elected leader Suu Kyi and much of her National League for Democracy (NLD) party leadership on Feb. 1, alleging fraud in a November election her party won in a landslide.

Having not been seen in public since her detention, Suu Kyi has a court hearing scheduled for Monday. She has been charged with illegally importing 6 walkie-talkie radios and of violating a natural disaster law by breaching COVID-19 protocols.

The coup, which brought a halt to tentative steps towards democracy after almost 50 years of military rule, has drawn hundreds of thousands of protesters onto the streets and the condemnation of Western countries.

US Secretary of State Antony Blinken denounced what he called “abhorrent violence” by security forces, while Canada’s foreign minister, Marc Garneau, said the military’s use of lethal force against its own people “appalling”. Both called for a united response.

The United Nations special rapporteur on human rights in Myanmar, Tom Andrews, said it was clear the junta’s assault would continue so the international community should scale up its response.

He suggested a global arms embargo, more sanctions from more countries on those behind the coup, sanctions on the military’s businesses and a UN Security Council referral to the International Criminal Court.

In a statement, Andrews said “words of condemnation are welcome but insufficient. We must act.”

“The nightmare in Myanmar that is unfolding before our eyes will get worse. The world must act.”

People marked the deaths of protesters with red and white roses, circling with yellow, white and pink flowers the spot in front of a school where one demonstrator was killed.

Small memorials were held for the victims, with candles lit in front of homes late on Sunday.