Polish President Andrzej Duda expressed dismay over the late-night arrest of two convicted lawmakers from the former ruling party holed up in the presidential palace even as he sought to calm a dramatic escalation of the political chaos that’s engulfed Warsaw.

The standoff between Duda, an ally of the Law & Justice party that was ousted from power last year, and Prime Minister Donald Tusk’s pro-European coalition lays bare the challenge the premier will have in efforts to dismantle eight years of nationalist rule.