Police imposed a curfew in Sri Lanka’s capital and surrounding areas on Friday, a day before a planned protest demanding the resignations of the country’s president and prime minister because of the economic crisis that has caused severe shortages of essential goods and disrupted people’s livelihoods.

Hours before the curfew announcement, police fired tear gas and water cannons to disperse thousands of protesting students wearing black clothes, holding black flags, shouting anti-governmental slogans, and carrying banners saying “Enough — now go.”

The protesters and other critics have said that President Gotabaya Rajapaksa is responsible for the economic crisis, the worst since the country’s independence in 1948. They also blame Ranil Wickremesinghe, who became prime minister two months ago, for not delivering on promises to end the shortages.

Civic and opposition activists have announced that thousands more protesters will gather in Colombo on Saturday. But the police announcement of the curfew said it took effect at 9 p.m. and will last until further notice in Colombo and its suburbs.

The curfew announcement drew criticism from government opponents and the Bar Association of Sri Lanka, which said the “curfew is blatantly illegal and a violation of the fundamental rights.”

The bar association statement asked police to immediately withdraw what the association called an “illegal order” imposing the curfew.

Opposition leader Sajith Premadasa called the curfew “a fraud.”

“Get on to the streets tomorrow. Defy the dictatorship and join with the people to make democracy victorious. Yes, we can,” he said in a tweet.

The U.S. Ambassador to Sri Lanka, Julie Chung, asked people to protest peacefully and asked the military and police “to grant peaceful protestors the space and security to do so.”

“Chaos & force will not fix the economy or bring the political stability that Sri Lankans need right now,” Chung said in a tweet.

Sri Lanka is nearly bankrupt and has suspended repayments of $7 billion in foreign debt due this year. It must pay back more than $5 billion annually until 2026. Its foreign reserves are nearly wiped out and it is unable to import food, fuel, cooking gas, and medicine.