Poland's Prime Minister Donald Tusk said on Thursday that border crossings with neighbouring Ukraine would be considered "critical infrastructure" to safeguard the passage of aid to the war-torn country.

"To ensure a 100 percent guarantee that military aid, equipment, ammunition, humanitarian and medical aid will reach the Ukrainian side without any delays, we will include border crossings with Ukraine... on the list of critical infrastructure," Tusk said after protests from Polish truckers and farmers caused lines at the Ukrainian border.