A peaceful rally in the Russian capital.

The singing sit-in is forced to move when a street cleaning truck is sent in.

In response, blogger Alexei Navalny calls on them to walk through Moscow in protest at electoral fraud and political leaders.

Parliament is expected to approve Dmitry Medvedev as prime minister Tuesday in a swap that returned Vladmir Putin to the presidency Monday.

(SOUNDBITE) (Russian) OPPOSITION LEADER AND ANTI-CORRUPTION BLOGGER ALEXEI NAVALNY SAYING:

"It's quite normal, we'll expand our presence here, I hope that in the morning there will be more people here, and many more people through the day. If the police start forcing us out, we are not going to scuffle with anyone, we will simply move to another place."

But the walk puts Navalny and fellow opposition leader Sergei Udaltsov back in detention just hours after they were released for an earlier protest.

Riot police have rounded up hundreds, including people in cafes wearing white ribbons in opposition against Putin.

(SOUNDBITE) (Russian) OPPOSITION SUPPORTER INNA KAREZINA SAYING:

"The people are uniting, and I think we managed to show, if not in the daytime then at night, that this is our city, that we can walk here with the white ribbons for which they detained us by daytime, and also express our view that we don't accept that inauguration (of Vladimir Putin)."

Although demonstrations have lost momentum in recent days, hundreds of protesters are trying to keep the pressure on Putin as he takes office for a third term.

Lindsey Parietti, Reuters