Outrage over the attack propelled Europe's leaders to condemn Russia and call for tougher measures on Moscow, like seizing frozen assets, further sanctions and increasing support for Ukraine's military.
"Everybody understands that, considering how (Russian President Vladimir) Putin is mocking the peace efforts, the only thing that works is pressure," said Kaja Kallas, foreign policy chief for the European Union.
At a meeting in Copenhagen on Friday, defence ministers discussed European troops' deployment in Ukraine to guarantee security and monitor a peace that seems distant, as American efforts to broker peace between Ukraine and Russia appear stalled.
Kyiv's European allies are looking to set up a force that could backstop any peace agreement, and a coalition of 30 countries, including European nations, Japan and Australia, has signed up to support the initiative.
Kallas said that in terms of security guarantees for Ukraine, the US is demanding that Europe carry "the lion's share" of the burden.
Military chiefs are figuring out how that security force might work.
The role that the US might play is unclear.
Trump has ruled out sending US troops to help defend Ukraine against Russia.
On Thursday, two missiles landed about 50 metres from an EU diplomatic mission in Kyiv, shattering the office's windows and doors but causing no injuries there.
The EU summoned Russia's envoy in Brussels, Karen Malayan, and told her that damages to the mission "are serious and constitute a violation of the Vienna Convention on Diplomatic Relations," said Anitta Hipper, an EU foreign policy spokesperson.
The UN Security Council scheduled an emergency meeting on air strikes against Ukraine on Friday afternoon at the request of Ukraine and five European council members — Britain, France, Slovenia, Denmark and Greece.
Two of Ukraine's top envoys were set to meet on Friday with the Trump administration regarding mediation.
White House press secretary Karoline Leavitt criticised both Putin and Ukrainian President Volodymyr Zelenskiy after Thursday's attack on Kyiv.
She said that Trump "was not happy about this news, but he was also not surprised".
Leavitt noted that Ukraine has also launched effective assaults on Russia's oil industry in recent weeks.
"Perhaps both sides of this war are not ready to end it themselves," Leavitt said.
"The president wants it to end, but the leaders of these two countries… must want it to end as well."
In Copenhagen, Kallas said defence ministers from across the 27-nation bloc discussed increasing sanctions on Russia and ramping up defence supplies to Ukraine's army.
At a news conference following the meeting, Kallas said that the ministers had discussed ways to work around Hungary's refusal to back Ukraine.
She said the EU has 6.6 billion euros ($A11.8 billion) blocked by Hungary's veto that could potentially be sent to Ukraine via NATO's new prioritised Ukraine requirements list approved by Trump.
On Thursday, the United States approved a $US825 million ($A1.3 billion) arms sale to Ukraine that will include extended-range missiles and related equipment to boost its defensive capabilities.
Lithuania's Defence Minister Dovilė Šakalienė said the attack on Kyiv on Thursday shows that hope now for peace is naive.
"All Putin is doing is really stalling, actually cheaply buying time to kill more people and to imitate sort of willingness to maybe stop his own murderous actions," she said.
She said Europe must deal with Russia more forcefully, like seizing frozen Russian assets.
