the street as riot-squad officers laid down a curtain of gas among the protesters, sending many stumbling away coughing and rubbing at their eyes.

Some protesters apparently gained a brief entry at Loto-Québec headquarters but were moved out. Others jostled a row of police bicycles, while some tossed objects at officers.

Students are protesting tuition increases pending later this year. (Alison Northcott/CBC) The melee was eventually brought under control with lines of police facing mobs of protesters across Sherbrooke Street, one of Montreal's main east-west arteries. Barriers and debris littered the street and a Quebec provincial police helicopter soared above the scene tracking the mob's movements.

Another group of students broke away and headed along nearby Ste-Catherine Street, the city's downtown shopping core, but no damage or ruckus was immediately reported.

Thestudents apparently tried to breach the Loto-Québec offices as part of a campaign of protests against higher tuition fees.

The scene in Montreal's streets illustrated the increasingly bitter battle over fees, pitting the Charest government against those who deem the province's rock-bottom tuition rates an inviolable principle.

It also served to underscore the intense student pushback that has discouraged Quebec governments of the past from increasing rates, which have remained frozen in the province for 33 of the last 43 years as authorities either avoided or abandoned plans for hikes.

Quebec tuition relatively low

Quebec's tuition rates for in-province students are the lowest in Canada, although students coming from other provinces pay higher rates.

Students looped around downtown Montreal, ending up on René-Lévesque Boulevard . (Peter Johnson/CBC) The provincial government says its planned