WARSAW, Poland (AP) — Poland reinforced its border with Belarus with more riot police, a day after groups of migrants tried to storm through a razor-wire fence on the eastern frontier where thousands have camped on the Belarusian side in the tense standoff. The European Union accuses Belarus President Alexander Lukashenko of using the migrants as pawns in a “hybrid attack” against the bloc in retaliation for imposing sanctions on the authoritarian government for a brutal internal crackdown on dissent. Polish authorities said the border was calm overnight, but they were bracing for any possibility. Belarus voiced concern about the buildup of Polish troops on the border.