Long lines of cargo trucks line Bulgaria's border checkpoints as ample snowfall and a strike in northern Greece have all but barred access to the country.

About 300 trucks have been stuck for more than 20 hours in Romania at Bechet, Bulgarian news agency BTA reported, after Bulgarian authorities have closed the other side of the border check-point at Oryahovo, saying that the road to Sofia was not fit for travel because of the massive snowfall.

The queue is more than 15km long, and growing. Some drivers have already run out of fuel, keeping their engines running to stay warm in the sub-zero temperatures at night, as well as food, BTA said.

Romanian authorities do not plan to let any trucks through until their Bulgarian counterparts open their side of the border, according to the report.

Traffic at the Vidin-Calafat border crossing has also been affected, but vehicles equipped for winter conditions are being allowed through, BTA said.

In southern Bulgaria, long-haul truck Greek drivers continued to blockade border check-points for a third straight day, but only against freight traffic, as buses and cars are allowed through.

About 40 trucks are stuck on the Bulgarian side of the Koulata-Promahon check-point, but traffic at the Ilinden-Exochi check-point, about 50km to the east of Koulata, was not affected, news agency Focus reported.

Greek drivers are protesting to persuade authorities to launch frequent checks on foreign trucks entering the country and to stop illegal immigrants sneaking onto their vehicles.

Inside Bulgaria, bad road conditions have prompted the Traffic Police to ban freight trucks from several major roads in northern Bulgaria: Vratsa-Oryahovo, Shoumen-Razgrad, as well as the roads linking the town of Rousse on the Danube River to Sofia, Varna and Silistra.