WARSAW (Reuters) -Poland may have to build a barrier on its border with the Russian exclave of Kaliningrad, a top Polish official said on Tuesday, as Warsaw suspects Russia plans to help African and Asian migrants cross over in the coming week. Poland accuses Russia and its ally Belarus of using migrants as part of a “hybrid warfare” campaign to destabilise Europe. With tensions running high due to the war in Ukraine, Poland fears a repeat of the 2021 crisis when thousands of African and Middle-Eastern migrants tried to cross the Belarus border. At that time, Minsk denied engineering the situa…