Police in Moscow have detained several dozen opposition activists who tried to stage a rally against newly inaugurated Russian President Vladimir Putin.

Russia's RIA Novosti news agency reported the arrests took place Wednesday near the Kremlin.

Moscow police have been tough on opposition members this week, starting with the detention of several hundred on the eve of Mr. Putin's inauguration to a historic third term as president on Monday.

Two prominent opposition leaders say they were each sentenced to 15 days in jail for their role in protests against Mr. Putin's return to the Kremlin.

Popular opposition blogger Alexei Navalny and coordinator of the Left-Wing Front movement Sergei Udaltsov were arrested late Tuesday with dozens of other activists participating in a protest near the Kremlin.

The two were charged with breaking rules on organizing demonstrations and marches.

Their arrests took place ahead of Russia's Victory Day parade, which commemorates Russia's 1945 defeat of Nazi Germany in World War II.

On Tuesday, Russia's lower house of parliament approved Dmitry Medvedev as prime minister after he was nominated by Mr. Putin. Mr. Medvedev has swapped jobs with Mr. Putin, who, until his inauguration Monday, was prime minister for four years.

Mr. Putin was elected to a third presidential term in March with 64 percent of the vote. He served as president from 2000 to 2008, but term limits prevented him from running for a third consecutive term. He then became prime minister under Mr. Medvedev.

A constitutional amendment has extended the president's time in office to two consecutive six-year terms, meaning Mr. Putin could stay in power until 2024 — an outlook many Russians find unsettling.