Russia launched more than 100 Shahed and decoy drones at Ukraine in nighttime attacks, the Ukrainian air force said Monday, after the Kremlin rejected an unconditional 30-day ceasefire in the more than 3-year war.

European leaders say Russia's failure to join a ceasefire offered by Ukraine would lead to further sanctions on Moscow.

The announcement was made by leaders of Britain, France, Germany, Poland and Ukraine after a meeting in Kyiv, and a phone call with President Trump.

They said that if President Vladimir V. Putin did not agree to the cease-fire, more sanctions would be imposed.

European Commission President Ursula von der Leyen on Saturday backed a proposed unconditional 30-day ceasefire in the Russian war in Ukraine and said that the EU was ready to impose more sanctions on Russia if a ceasefire is breached.

The ultimatum from Berlin comes as Ukraine said Russia was still carrying out attacks along the front line, despite a ceasefire proposal agreed on the weekend among Kyiv's allies for a 30-day ceasefire to start Monday. The Kremlin said such an ultimatum "is unacceptable for Russia."

The Kremlin brushed off the threat of further sanctions, saying that “the language of ultimatums is unacceptable.”