Bulgarian border police authorities said on Wednesday they had prevented a total of 13 groups of migrants from entering Bulgaria in 24 hours.

Two of the groups had tried to cross into the country from Greece, near the Novo Selo border crossing point in Southeastern Bulgaria.

Among the 256 people who sought to enter, some were hidden in cargo vehicles. In two such developments, drivers were arrested after migrants with no documents were found in their respective cargo compartments.

This comes amid increased migratory pressure at Bulgaria's border with Turkey and, more recently, Greece.

Last week a migrant died in an incident involving border police officers, some 30 km into Bulgarian territory.