At least 21 people were killed and 48 injured by shelling in the Kherson region on Wednesday, Ukrainian officials said, as the death toll continues to rise.

A railway station and market in the city of Kherson were hit in strikes, which occurred across the Kherson region in southern Ukraine, officials said.

"A railway station and a crossing, a house, a hardware store, a grocery supermarket, a gas station -- do you know what unites these places? The bloody trail that [Russia] leaves with its shells, killing civilians in Kherson and Kherson region," Ukrainian President Volodymyr Zelenskyy said on Twitter.

All the victims were civilians, Zelenskyy said.

An ambulance was also damaged in the strikes, according to Ukrainian Prosecutor General Andriy Kostin.

"No military objects here. Just civilians, including children," Kostin said on Twitter.

At least one person was killed and three injured in the strike on the railway station, officials previously said.

The Biden administration has announced a new $300 million military aid package for Ukraine.

The package includes additional ammunition for U.S.-provided High Mobility Artillery Rocket Systems, as well as "additional howitzers, artillery and mortar rounds, and anti-armor capabilities that Ukraine is using to push back against Russia’s unprovoked war of aggression," the Department of Defense said in a statement.

This marks the Biden administration’s 37th drawdown of equipment from Defense Department inventories for Ukraine since August 2021.

Ukrainian President Volodymyr Zelenskyy rejected Russia's claim that his country was involved in the drone attack on the Kremlin early Wednesday.

Zelenskyy, who is currently in Finland, said the claim was the prelude to a "large-scale terrorist attack" from Russia.

"First of all, Ukraine wages an exclusively defensive war and does not attack targets on the territory of the Russian Federation," Zelenskyy said in a statement. "What for? This does not solve any military issue. But it gives RF grounds to justify its attacks on civilians."

Zelenskyy went on to say that various attacks in Russia could be the result of "guerrilla activities of local resistance forces."

Russian President Vladimir Putin's spokesman has accused Ukraine of trying to strike Putin's residence in the Kremlin with two drones overnight, but said they were brought down before they could reach their target.

No injuries were reported, Kremlin officials said. Putin was not at the residence at the time, they said.

Videos released on official social media channels appeared to show a drone strike the roof of the Senate Palace at the Kremlin.

The Kremlin said that "the Russian side reserves the right to retaliate whenever and wherever it deems necessary."

-ABC News' Patrick Reevell and Tanya Stukalova

The United States announced an additional $2 billion military aid package for Ukraine on Friday, as the Eastern European country marks the one-year anniversary of Russia's full-scale invasion.

The new aid package includes more missiles for Ukraine's U.S.-supplied High Mobility Artillery Rocket Systems (HIMARS), additional 155mm artillery ammunition, more Switchblade one-way drones and other military equipment, according to the U.S. Department of Defense.

"One year into a war of aggression waged by a permanent member of the U.N. Security Council, our allies and partners worldwide stand united and resolute," U.S. Secretary of Defense Lloyd Austin said in a statement. "Putin's reckless, illegal war is not just an all-out assault on Ukraine's sovereignty and a historic threat to European security. It is also a direct attack on the system of rules, institutions, and laws that the world built at such great cost after World War II -- a system that rejects aggression and respects the rights of all countries, big and small."

The additional aid is being provided under the Ukraine Security Assistance Initiative (USAI) plan, meaning this equipment and artillery have to be made from scratch before being delivered, which will take time. This is different from the other aid packages that come from existing U.S. military stockpiles and get delivered faster.

With the new aid package, the Biden administration has now provided $31.8 billion in assistance to Ukraine since Russia's war began on Feb. 24, 2022.

"Putin thought that Ukraine’s defenses would collapse, that America's resolve would falter, and that the world would look the other way. He was wrong," Lloyd said. "One year later, Ukraine's brave defenders have not wavered, and neither has our commitment to support them for as long as it takes. Despite the Kremlin's campaign of cruelty, the people of Ukraine have shown stunning bravery, skill, and fortitude. Today and every day, we stand by the courageous Ukrainians fighting to defend their country, and we mourn with those who have lost their loved ones in Moscow's monstrous and unnecessary war."

"Difficult times may lie ahead, but let us remain clear-eyed about what is at stake in Ukraine," he added. "And let us remain united in purpose and in action -- and steadfast in our commitment to ensure that a world of rules and rights is not replaced by one of tyranny and turmoil."

-ABC News' Luis Martinez