Poland convenes NATO meeting after deadly explosion reportedly caused by Russian missile
Government spokesperson says 2 killed in blast but doesn't confirm missile strike
attacked country by taking "such action as it deems necessary, including the use of armed force."
However, each country has no obligation to respond militarily.
Russia denies responsibility
In Washington, the Pentagon, White House and U.S. State Department said they could not corroborate the report and were working with the Polish government to gather more information. The State Department said the report was "incredibly concerning."
Germany said it was monitoring the situation, and Norway said it was seeking details.
Russia's Defence Ministry denied that Russian missiles hit Polish territory, describing reports as "a deliberate provocation aimed at escalating the situation."
It added in a statement: "No strikes on targets near the Ukrainian-Polish state border were made by Russian means of destruction."
The Kremlin did not immediately respond to requests for comments.
Russia was pounding cities across Ukraine with missiles on Tuesday, in attacks that Kyiv said were the heaviest wave of missile strikes in nearly nine months of war. Some hit Lviv, which is less than 80 kilometres from the border with Poland.
With files from Reuters and CBC's John Mazerolle