A video of a woman being struck in the face by a stranger outside a Paris cafe has sparked nationwide outrage in France amid a government crackdown on sexual harassment.

Key points: Student Marie Laguerre is calling for more action against sexual harassment after footage of her attack went viral

Student Marie Laguerre is calling for more action against sexual harassment after footage of her attack went viral France has moved to introduce on-the-spot fines for sexual harassment

France has moved to introduce on-the-spot fines for sexual harassment The first fines are expected to be handed out in September

The video, posted to Facebook by student Marie Laguerre, shows her walking past a restaurant in Paris's north-east.

Walking briskly behind her is a bearded man in a black T-shirt with his jacket slung over one shoulder.

Ms Laguerre said the man made "dirty noises/comments/whistles" and spoke to her "in a provocative way" as she passed him.

"I felt hatred," Ms Laguerre told Le Parisien.

"I refused to be demeaned, it was humiliating. I refused to look down, I looked him right in the eyes, I was not going to apologise."

Ms Laguerre shared CCTV footage obtained from the cafe on her Facebook page. ( Facebook: Marie Laguerre )

CCTV footage shows Ms Laguerre then shouting something at the man, who appears to throw an ashtray from afar.

"I let out a, 'Shut up!' while making my way," she wrote on Facebook.

"Because I do not tolerate this type of behaviour.

"I cannot keep silent and we must not be silent."

The man then approaches her and without warning hits her in the head, shocking patrons on the cafe's patio.

Ms Laguerre said the brazen attack left her with swelling in her cheeks.

Marie Laguerre said the attack left her with swelling around the cheek bones. ( Facebook: Marie Laguerre )

"I was in pain, but it happened in a few seconds so I did not realise it right away," she said.

The 22-year-old student has now called for a clampdown on sexual harassment after footage of the attack went viral.

According to France 24, the Paris public prosecutor's office has opened an investigation after Ms Laguerre lodged a complaint.

'It has to be stopped from the beginning': Equalities Minister

The footage has bolstered the French Government's crackdown on sexual harassment.

In March, the Government announced sexual harassment on French streets or in public transport will be punished by an on-the-spot fine of 90 euros ($140).

The first fines are expected to be handed out in September, according to Equalities Minister Marlene Schiappa, who said she was outraged by the attack on Ms Laguerre.

"The video illustrates the continuum of gender and sexual violence," Ms Schiappa told France's 24-hour news channel, BFM.

"It starts with obscene noises, then cries and then insults and threats and then a blow.

"It has to be stopped from the beginning, that is why we are voting on the verbalisation of street harassment."

Ms Schiappa also said more than 1 million euros had been allocated for action against gender-based violence in the workplace.

"This issue is serious [it is about] the freedom of women to circulate freely in the public space," she said.

The fines have resonated among French women as the #MeToo movement and its French equivalent #BalanceTonPorc ("rat on your pig") have gathered pace.

Ms Laguerre wrote on her Facebook page: "This is not the only incident. Harassment is everyday.

"To those men who think anything goes in the street, who allow themselves to humiliate us and who can not stand being offended, it is unacceptable.

"It is time for this kind of behaviour to STOP. #AllWomenTogether."