MONTREAL — There were four arrests on the ground and the whiff of pepper spray in the air Thursday as hundreds of protesters took to the streets of Montreal against planned university tuition increases.

Students, unions and women's groups held a joint protest in a downtown area around the local stock exchange, as access to a hotel was cut off.

Riot police were called in and things became tense as officers unloaded the contents of pepper spray cans into the crowd.

Four demonstrators were arrested and carted away in police vehicles, which caused other participants to attempt to block the vehicles' path while chanting for their release. A cameraman from one TV network was surrounded by protesters who shouted at him.

Tens of thousands of university students are also planning strikes in a throwback to the kind of protests in the 1990s that kept the then-Parti Quebecois government from raising attrition fees. Student rates have been largely frozen in Quebec, for most of the last 40 years.

But the current Liberal government of Jean Charest wants to change that.

Quebec's university tuition fees are so low that, even with an annual $325 hike planned over the next five years -- which would nearly double current rates -- they would still be the lowest in the country.

The protesters argue, however, that the increase will keep some people from obtaining a higher education and they call it a question of societal values.

Police said those arrested Thursday could face charges of obstructing justice or refusing to comply with police.