Dozens of riot police marched into Harvard Square again last night just before the Summerthing concert in the Stadium ended. Traffic was not allowed to enter the Square.

A little over an hour later, the bulk of the crowds had left the Square, and the riot-clad police marched out, taking their dogs and tear-gas guns with them.

Dozens of shirt-sleeved police with clubs remained behind, in the usual heavy post-concert presence.

Anonymous leaflets calling for trashing had reportedly been circulated during the day.

Lamont Library closed early.