The boosted security mode is supposed not to let any explosives, weaponry or ammunition be brought to Ukraine; it is also supposed to keep the persons with separatist and extremist views away from coming to Ukraine. This especially concerns bikers, first of all, those representing Night Wolves, the infamous pro-Russian biker gang.
The measures are taking place based on the analysis from the previous years; in 2017-2018, Night Wolves and their followers attempted to cross the Ukrainian border while on their way to the EU.
Ukraine's State Border Guard added that no organized biker gangs crossed the border during Easter holidays. In case any such extremist or pro-Russian formations try to cross the border, they will be denied from doing so, within the order foreseen by the Ukrainian law.