KYIV, Ukraine (AP) -- Russian forces bombarded the southern Ukrainian city of Zaporizhzhia with rockets overnight, wounding 20 people, including four children, President Volodymyr Zelenskyy said Tuesday as he urged European leaders to make the continent safe by building an ambitious air defense umbrella.

With the war grinding on since Russia's full-scale invasion of its neighbor more than 3½ years ago, there has been no let-up in Russian strikes on civilian areas of Ukraine and its army's push on the roughly 1,000-kilometer (620-mile) front line.

A settlement to end the war appears to be no closer despite months of U.S.-led peace efforts. U.S. President Donald Trump's ultimatums and deadlines for Putin to engage with proposals to stop the fighting have passed without obvious consequences.

Just over the past two weeks, Zelenskyy said on Telegram, Russia has launched more than 3,500 drones, more than 2,500 powerful glide bombs and almost 200 missiles at targets inside Ukraine.

Russian glide bombs, usually dropped by jets at high altitude and far behind the front line, and drone swarms are a major challenge for Ukrainian defenses. Glide bombs aren't very accurate, but they leave big craters, and Ukraine has no effective countermeasure against them.

Russian drones also recently landed on Polish soil, prompting NATO to beef up the alliance's European air defenses as tensions with Moscow mounted.

"Now is the time to implement the joint protection of our European skies with a multilayered air defense system. All the technologies for this are available," Zelenskyy said on Telegram. "We need investments and desire, we need strong actions and decisions from all our partners."

In Zaporizhzhia, the Russian barrage struck more than 20 apartment buildings, starting fires, regional head Ivan Fedorov said on national television.

"We hadn't yet recovered from enemy strikes on Aug. 30. We are currently repairing those buildings, those windows, but now the enemy has added more work for our municipal workers," Fedorov said.

Russia also hit a civilian logistics center in the Kyiv region, Zelenskyy said. He also posted on Telegram a video of a Russian drone striking the northeastern city of Kharkiv, where officials said that four people were wounded as the National Pharmaceutical University in the city center was hit.

Zelenskyy repeated his appeal for countries to tighten their economic sanctions on Russia.

"The only reason Russia can allow all this is that it doesn't feel any pain," Zelenskyy wrote on social media. "Until Russia experiences truly severe losses -- above all economic ones -- it will avoid genuine diplomacy and an end to the war."

In response to Russia's attacks, Ukraine has developed its own long-range drones that have hit deep inside Russia, damaging installations vital for Russia's war effort.

Recent strikes have included oil refineries, depots and terminals. Russia remains the world's second-largest oil exporter, but a seasonal rise in demand and sustained Ukrainian drone strikes have caused gasoline shortages in recent weeks.

Ukraine's General Staff said Tuesday that the armed forces struck an oil refinery in the Saratov region of western Russia during the night. Explosions and a fire were reported at the facility, the General Staff said on its Facebook page.

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