Violence broke out at the Singhu border protest site after large groups of people claiming to be locals reached there to vacate the area, leading to a clash between them and agitating farmers and prompting police to resort to baton charge and use tear gas shells.

Delhi Police SHO (Alipur) Pradeep Paliwal was injured in the violence after a man attacked him with a sword, an official said, adding that some people were also wounded.

The official said that police detained the man who attacked the station house officer.

The locals demanded that the farmers vacate the Singhu border protest site as they had "insulted" the national flag during their tractor parade on Republic Day.

Armed with sticks, the group of locals reached the site and asked the farmers to leave while raising slogans against them. Both sides also pelted stones at each other. The protestors at the Singhu border, much of which is barred for entry from outside, were coming out in numbers to resist the locals.

However, they were promptly stopped by farmer union volunteers which helped the situation from turning ugly.

"They are not locals, but hired goons. They were throwing stones, petrol bombs at us. They attempted to burn down our trolleys also. We are here to resist them. We won't leave the place," said Harkirat Mann Beniwal, 21, from Punjab's Khana district.

The security forces turned the border into a fortress on Friday by arranging multi-layered security, putting barricades everywhere and sealing all entry points. The nerve-centre of the ongoing farmer's protest is being thronged with thousands of security personnel marching at the site.

No one, even media personnel, are being allowed to enter the protest site with the area cordoned off by multiple concrete barricades and intermodal containers.

"These batons, tear gas shells and ammunition can't scare us. We won't budge, we won't leave till our demands of repealing three farm laws are met," said 26-year-old Manjeet Dhillon, from Haryana's Kaithal, while standing on the other side of the barricade.

While there was a sense of unease among some protestors, nothing changed at the respective stages of the Samyukta Kisan Morcha (SKM) and the Kisan Mazdoor Sangharsh Samiti (KMSC), where decibel levels, courtesy the fiery speeches, were high like before.

The SKM has blamed the KMSC, actor-turned-activist Deep Sidhu and the central government for the violence during the farmers' tractor parade in Delhi on January 26.

Ram Bhados, the only shop open at the whole stretch, said he opened it after being asked to do so by the security forces.

"I didn't want to open the shop. I am afraid things might get violent. They (the security personnel) asked me to open the tea-shop and serve them. They said they'll protect me," said the visibly-tensed 18-year-old.

The tractor parade on Tuesday that was to highlight the demand of the protesting farmer unions for a repeal of three new agriculture laws turned violent as the protesters deviated from the pre-designated routes, attacked police personnel, overturned vehicles and hoisted a religious flag on the ramparts of the iconic Red Fort.

The police issued lookout notices against farmer leaders on Thursday and announced a probe into the "conspiracy" behind the Republic Day violence.

The police have so far registered 33 FIRs in connection with the violence and issued lookout notices against 44 people, including most of the farmer leaders.