Julija Samorokovskaja, a Vilnius police spokeswoman, told BNS a "tractorcade" of 51 vehicles, escorted by police, was moving along the capital's streets.
According to Ignas Jankauskas, head of administration of the Association of Lithuanian Grain Growers, around 2,000 to 3,000 tractors were expected to join the protest.
In the district of Kaunas, some 150 tractors were parked at 11 a.m. on several roads leading to the Via Baltica and A1 motorways.
"This is a warning protest that started with the green cross initiative and has brought farmers together," he told BNS. "We want to show the authorities that farmers are united."
Farmers demand that taxes are not increased until the direct payments they receive reach the EU average.
Farmers started their protest in mid-November by erecting green crosses in their fields.
According to Jankauskas, around 10,000 such crosses have been erected across Lithuania.