President Francois Hollande has condemned displays of homophobic violence in France, as the country looks set to legalise same-sex marriage and adoption rights for gay couples.

“Homophobic acts, violent acts have been committed. The right to protest is recognised by our constitution and accepted by the French. But no protest must degenerate,” President Hollande said on Thursday.

He was speaking after France’s Interior Ministry confirmed that four people had been detained on suspicion of carrying out an attack at a gay bar in Lille.

The owner linked the incident to “tensions” over the country’s proposed same-sex marriage bill, which is close to final approval.

It was approved by the French Senate last week after being voted through the lower house earlier this year.

The bill has now gone back to the National Assembly for a second reading, and could face a final vote as early as Tuesday.

There is growing concern at the recent spate of homophobic incidents in France.

In the past week, several anti-gay protests have turned violent in cities across the country.

On Wednesday, a several-thousand-strong protest in the streets of Paris turned ugly with cars and public property vandalised and police officers and journalists attacked.

Interior Minister Manuel Valls is due to hold a meeting with representatives of security forces in order to “reinforce security measures surrounding protests following the excesses of the past days”.

He has pledged to prevent further homophobic assaults.

French Prime Minister Jean-Marc Ayrault has also condemned the violence and has called for calm.

“These protests have a right to take place, we are in a republic. But calls for violence, calls to hate, must be condemned,” he said on Thursday.