WASHINGTON -- Dozens of people were arrested Wednesday during a chaotic and often tense day of protests as the Occupy movement blockaded intersections and snarled traffic downtown for hours.

Hundreds of protesters from Occupy D.C. and around the country joined in the "Day of Action: Occupiers Unite," targeting K Street NW, long a symbol of the nation's lobbying industry because of the numerous lobbying firms based there.

A District of Columbia police commander estimated that 50 to 70 people had been arrested, many of them charged with obstruction of a public highway, but he cautioned that the figure was preliminary.

Protesters filled K Street as a cold rain fell, chanting slogans while slogging through puddles and blocking intersections along K Street between 14th and 16th streets. They blocked intersections with newspaper boxes, wooden pallets, office furniture and tents.

Tempers frayed and horns blared.

Occupy D.C. protesters marched and chanted in front of the Podesta Group, the lobbying firm co-founded by John Podesta, President Bill Clinton's former chief of staff, as employees took pictures of them from behind the windows above.

Other protesters went to Capitol Hill to disrupt and chant in front of congressional offices and even at Charlie Palmer Steak, a favorite restaurant of the D.C. elite.