WARSAW—Poland accused Belarus on Wednesday of staging an armed cross-border intrusion and said it had summoned the Belarusian charge d’affaires to protest over what it said was “a deliberate escalation” of the migrant crisis at the frontier. Belarus rejected the allegation as unfounded and intended to sully its image. Minsk also denies Polish and European Union accusations that it is deliberately encouraging illegal migrants to enter Poland and other EU states via Belarusian territory. Poland has imposed a state of emergency at the border to stem a surge in the number of migrants from countries such as Afghanistan and Iraq trying to enter its territory via Belarus. Poland’s foreign ministry said unidentified uniformed individuals armed with long guns had crossed into Polish territory from Belarus on the night of Monday, Nov. 1. “Deputy Foreign Minister Piotr Wawrzyk forwarded an emphatic protest … against the violation of the Polish state border, …