Ukrainian President Volodymyr Zelenskyy said Thursday that Ukrainian experts will participate in a probe of the deadly projectile falling in southeastern Poland, the Interfax-Ukraine news agency reported.

"Yesterday, we received confirmation that our specialists will participate in the investigation. Until the investigation is completed, we cannot say for sure which missiles or their parts fell on Polish territory," Zelenskyy said.

On Tuesday, about 100 missiles were fired by Russia against Ukraine, Zelenskyy said, voicing his belief that some of those missiles could have crossed the Ukrainian-Polish border.

"We have seen pictures of funnel diameter. It could not be only the remnants of anti-missile systems," he said.

Russia's Defense Ministry has denied reports that Russian missiles had hit Polish territory, describing them 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."

Wreckage reportedly found at the scene "has nothing to do with Russian weapons," it said.

On Wednesday, Oleksiy Danilov, the secretary of Ukraine's National Security and Defense Council, said that Kiev requested access to the site of the explosions in Poland for representatives of Ukraine's Defense Ministry and the State Service for Emergencies.

Ukraine has evidence of a "Russian trace" in the explosion in eastern Poland, which Warsaw and the North Atlantic Treaty Organization say was probably caused by a Ukrainian air defense missile, Danilov said, without giving any details.

On Tuesday, two Polish citizens were killed by the projectile falling in the Polish village of Przewodow near the Poland-Ukraine border.

U.S. President Joe Biden said on Wednesday that the missile blast in eastern Poland was likely not an attack from Russia but was caused by a Ukrainian air defense missile.

(With input from Xinhua and Reuters)