MOSCOW — On the same day that President Vladimir Putin gave a nationally televised speech warning the West against threatening Russia, the homegrown opposition to his increasingly hard-line rule returned to the streets.

Tens of thousands of people protested in cities across the country Wednesday for the first time in two months, responding to calls to support jailed Kremlin critic Alexei Navalny as his allies warn that his health is failing and his entire activist network could be outlawed soon.

The last time such demonstrations took place — in January and February, right after Navalny was arrested — major crowds turned out, and more than 11,000 people were detained, according to independent rights monitors.

The Kremlin's crackdown has grown more intense in the months since, targeting independent journalists, human rights organizations and Navalny's associates. Wednesday's rallies, though smaller than the demonstrations earlier in the year, were a show of defiance.

"In our constitution, at the very beginning, it says we have freedom, but in reality we don't," said Anna, a 19-year-old student at the protest in Moscow, who like others spoke on the condition that only her first name be used because the demonstrations are considered illegal by authorities.

The government is "stomping on our throats to keep us silent," she said. 

Navalny's team hasn't announced plans for future protests, and its future is uncertain. Prosecutors have requested that Navalny's network of regional offices and his Anti-Corruption Foundation be added to a list of "terrorist and extremist" groups, clearing the way for its members to be jailed.

That means Wednesday's demonstrations could be the last before Navalny's group is forced underground.

One independent Russian news outlet estimated 25,000 people came to Moscow's demonstration. After the start of the rallies in Moscow and St. Petersburg, Russia's two largest cities, about 1,500 people had been detained, the monitoring group OVD-Info said.

Marchers chanted "Putin is a thief," "Freedom to political prisoners" and "Let him go," in reference to Navalny, who suffered a near-fatal poisoning from a nerve agent in August. He blamed the attack on Putin's agents — an assertion backed by Western officials. The Kremlin denies any role.

Video on social media showed Navalny's wife, Yulia Navalnaya, in a crowd of protesters chanting her name.

In Moscow, riot police didn't immediately move to break up the demonstrations. In St. Petersburg, social media video purported to show police officers using stun guns on some protesters.

Some protests overlapped with Putin's annual state-of-Russia address in Moscow. In the far-eastern city of Khabarovsk, near Russia's border with China, video on social media purported to show protesters in a square surrounded by armored vehicles and lines of masked riot police. Putin's address was broadcast on a giant screen, and the person filming the video said authorities had turned up the volume.

Galina, an 80-year-old protester in Moscow, said Putin has taken "all our hopes and dreams" of different leadership. Constitutional changes now allow Putin to potentially stay in power another 15 years.

Putin devoted the majority of his speech to promising better times ahead and more government support for Russians facing economic hardships. But he saved his most fiery remarks for the end, with a message for the international community: Anyone who threatens Russia "will regret it like they've never regretted anything before."

His warnings to the West come amid tense relations with Moscow on several fronts.

Russia's recent military buildup along the Ukrainian border has been widely criticized. But despite the redeployment of forces around Ukraine, which has been at war with Russia-backed separatists for seven years in the eastern Donbas region, Putin didn't announce any new moves, barely referring to Ukraine at all.

Meanwhile, the United States imposed economic sanctions on Russia last week in response to a cyberespionage campaign and efforts to influence the presidential election. Then on Monday, the Biden administration vowed "consequences" for the Kremlin if Navalny dies in prison, as his allies have raised alarms about his failing health.

“We don’t want to burn bridges, but when someone views our good intentions as indifference or weakness and intends to blow up these bridges in turn, they must know Russia’s response will be asymmetrical, swift and harsh,” Putin said Wednesday.

“I hope no one will cross the red line in regards to Russia. And where this red line will be drawn, we will decide for ourselves,” he added.

Navalny is serving a more than two-year sentence in a penal colony east of Moscow. He is three weeks into a hunger strike, demanding access to a doctor at his own expense, and his personal physician said Navalny’s health has deteriorated so much that he “could die at any moment.”

Blood tests revealing high potassium levels were indicative of kidney failure, and severe heart rhythm disturbances threatened cardiac arrest, Navalny’s doctor, Yaroslav Ashikhmin, said in a Facebook post.

On Sunday, Navalny was transferred to a prison hospital in a different site. He said he received a glucose drip.

In an Instagram post Tuesday, Navalny thanked his supporters. He has no access to the account, but lawyers have regular contact with him, and posts are made by his team.

“I laughed when I read the quotes from the luminaries of medicine, that with such a level of potassium, as in my tests, I should be either in intensive care or in a coffin,” the post said. “You can’t take me that easily.”

Although Navalny’s allies initially said they would announce new demonstrations once their online database reached 500,000 signatures, Navalny’s poor condition meant they couldn’t wait any longer, a statement on his website said.

“Things are developing too quickly and too badly,” his allies wrote. “An extreme situation demands extreme decisions.”

Two of Navalny’s allies in Moscow who were already under house arrest, top aide Lyubov Sobol and press secretary Kira Yarmysh, were detained before lunchtime.

“The detention of supporters of Alexei Navalny in advance of planned protests in Russia today are deplorable. Authorities must respect the right to assembly,” European Council President Charles Michel wrote on Twitter on Wednesday.

Dmitri, a 48-year-old protester in Moscow, said that “Russia is in the Dark Ages. In the past 25 years, the country has been completely destroyed.”

He added that he came to Wednesday’s protest because of his two children.

“I want them to live in a good and normal country,” Dmitri said.

Mary Ilyushina contributed to this report.