Nearly 700 people have been detained in two Quebec cities in the biggest single night of mass arrests since student protests over fees began in February.

Police invoked a controversial new law designed to curb demonstrations as they detained 518 people in Montreal and another 176 in Quebec City.

The protests against a planned rise in tuition charges escalated after Bill 78 passed last week.

The Quebec government insists it will not change its mind on the fee hike.

The march in Montreal late on Wednesday began peacefully, as several thousand demonstrators flooded the central square of Quebec's largest city.

Police later penned in the protest - adopting a controversial European police tactic known as "kettling" - after reporting they had been pelted with rocks and other projectiles.

Those arrested were released on Thursday and issued with fines of more than C$600 (£370), AFP news agency reports.

Authorities invoked Bill 78, which requires eight hours notification before public demonstrations.

Bill 78, passed last Friday, requires marches to follow pre-approved routes, but protesters say it infringes their democratic rights, and have pledged to legally contest it.

Since the passing of the public assembly law, more than 300 people were arrested overnight at a protest in Montreal last Sunday and another 100 were detained in the city on Tuesday.

Quebec currently has the lowest tuition rates in Canada, but the government's proposal would raise the fees by 80%, in increments of $254 per year (£160) for seven years.

Talks between the government and student unions have broken down several times.