Detentions made at Moscow pro-Navalny demo

Thousands of people took to the streets on Sunday across Russia's vast expanse to demand the release of jailed opposition leader Alexei Navalny, keeping up a wave of nationwide protests that have rattled the Kremlin. Hundreds were detained by police.

The authorities mounted a massive effort to stem the tide of demonstrations after tens of thousands of people rallied across the country last weekend in the largest and most widespread show of discontent Russia has seen in years.The 44-year-old Navalny, an anti-corruption investigator who is the best-known critic of President Vladimir Putin, was arrested on January 17 upon returning from Germany, where he spent five months recovering from nerve-agent poisoning that he blames on the Kremlin.

Russian authorities have rejected the accusations.On Sunday, police detained over 400 participants in protests held in many cities across Russia's 11 time zones, according to the OVD-Info, a group that monitors arrests.

In Moscow, the authorities introduced unprecedented security measures in the city center, closing subway stations near the Kremlin, cutting bus traffic and ordering restaurants and stores to stay closed.Navalny's team initially called for Sunday's protest to be held on Moscow's Lubyanka Square, home to the main headquarters of the Federal Security Service, which Navalny claims was responsible for his poisoning.

After police cordoned off the area around the square, protest organizers urged demonstrators to gather at another central square a mile away.Police showed up in force at that location too, detaining some protesters and putting them into buses.