Protesters at the G20 meeting in Pittsburgh have been met my an overwhelming and thoroughly militarized police response. Here's a video gallery of some on-the-ground confrontations yesterday and overnight.

Protesters at events like these are in many cases self-defeating and deliberately confrontational. But some of these videos look like outtakes from Children of Men. There are police in riot gear literally marching in lock-step formation ("Left! Left! Left, right, left!"), the apparent use of sonic weapons to disperse crowds, and an omnipresent creepy voice over a loudspeaker declaring, "By order of the Pittsburgh chief of police, I declare this an unlawful assembly." Last night, students at the University of Pittsburgh, including bystanders apparently hanging out news their student union, were gassed by riot police.

So far today, protests appear to have gone without much incident, at least according to the Pittsburgh Post-Gazette's G20 blog.

Police deploy acoustic weapons.

Firing teargas and—reportedly—rubber bullets on University of Pittsburgh students last night.

More teargas and confrontations with University of Pittsburgh students, some of whom claim not to have been protesting.

An arrest yesterday.

Riot police taking down a woman who appears to be antagonizing them.

CNN reporter teargassed yesterday.

This video, linked on the Drudge Report, appears to show a protester being hauled away by military servicemembers in an unmarked car. Some right-wing bloggers are calling bullshit on it, noting inconsistencies in their uniforms and speculating—not without warrant—that performance-artist protesters might be interested in staging an incident like this.