Trucks lined up at the border checkpoint in Dorohusk, with almost all cargo traffic blocked by protesters who blamed the liberalisation of European Union rules for the slump in their revenues.

"We want the rules of fair competition to be restored," Rafal Mekler, a co-organiser of the protest, told AFP in Dorohusk.

Clad in neon safety vests, a group of protesters led by Mekler had left their trucks parked on the main road to the Dorohusk checkpoint, effectively blocking the route.

On the vehicles, a banner detailed the protesters' demands, with reinstating entry permits for their Ukrainian rivals at the top of the list.

Following Russia's full-scale invasion of Ukraine, the EU waived a system of permits for Ukrainian transport companies to enter the bloc.

The Polish companies claim the move has triggered an influx of Ukrainian competitors into the sector, plunging their profits.

"Their costs of servicing a truck, hiring a driver or merely of opening a business or paying social insurance are much lower," Marek Oklinski, a transport company owner, told AFP in Dorohusk.

"They drive the prices down and take the cargo that we used to carry," he added.

Oklinski has had 25 years of experience carrying goods to Ukraine, but according to him and his fellow truckers, the competition with Ukraine is now proving too difficult to endure.

Ukraine said the protest was damaging to both countries.