Ukraine's president says any negotiations with Russia on issues related to the ongoing invasion must take place in public.

Volodymyr Zelenskyy told media representatives on Wednesday that he had received certain signals from the leaders of other countries regarding possible negotiations with the Russian side.

Zelenskyy said Russia is waging a "full-scale aggressive war" against Ukraine, so any negotiations "must take place in public, not behind closed doors."

Zelenskyy's remarks appear to represent a delicate balancing act. Other countries have urged him not to completely shut the door to negotiations.

Zelenskyy has not rejected the calls outright, but observers say he has effectively ruled out talks with Moscow by asking for public negotiations, because that is a condition Russia is unlikely to accept.

Meanwhile, Ukraine says the experts it sent to Poland to investigate a missile explosion have arrived in the village. The incident occurred on Tuesday and left two people dead.

Ukraine's Foreign Minister Dmytro Kuleba tweeted on Thursday that Kyiv expects Polish law enforcement officials to swiftly help the experts gain access to the site.

The United States and other Western nations say the explosion close to the border with Ukraine may have been caused by a Ukrainian air defense missile. Kyiv disputes the assertion.