Two-thirds of residents have fled eastern Ukraine's Donetsk Oblast since the start of Russia's invasion in late February, according to the regional governor.

Speaking to Ukrainian media on Tuesday, Donetsk Oblast Gov. Pavlo Kyrylenko said some 350,000 residents remain in the war-torn region.

During his Tuesday evening address, Ukrainian President Volodymyr Zelenskyy called the hostilities in Ukraine's east "hell."

"It cannot be described with words," Zelenskyy said.

Ukrainian forces cannot yet "completely break the Russian army's advantage in artillery and manpower, and this is very noticeable in the fighting," he added.

Last month, Ukrainian Deputy Prime Minister Iryna Vereshchuk said 200,000 civilians must be evacuated from the Donetsk Oblast before the weather gets colder, as there is no proper electricity or gas supply in the area for residents to heat their homes. Russian forces are also destroying heating equipment, according to Vereshchuk.

Zelenskyy has ordered the mandatory evacuation of Donetsk Oblast residents, urging them to leave as soon as possible. Those who comply will be compensated.

"The more people leave [the] Donetsk region now, the fewer people the Russian army will have time to kill," he said.

Although many refuse to go, Zelenskyy stressed that "it still needs to be done."

Mandatory evacuation from Donetsk Oblast began on Aug. 1. The first two trains evacuated 224 people to the central Ukrainian city of Kropyvnytskyi, according to local officials.

-ABC News' Edward Szekeres, Yulia Drozd, Fidel Pavlenko and Yuriy Zaliznyak

A ship carrying 27,000 tons of corn has left the Ukrainian port of Odesa and is expected to arrive in Turkey on Wednesday, according to a statement issued by the Joint Coordination Centre, Black Sea Grain Initiative.

The ship, adorned with the flag of Sierra Leon, left Odesa on Monday morning and is ultimately destined for Lebanon, according to the JCC.

The route will follow a humanitarian corridor, the JCC said.

The JCC is responsible for carrying out inspections on inbound and outbound vessels in Istanbul to ensure there is no unauthorized crew or cargo, according to the statement.

The arrival of the shipment from Ukraine is a beacon of hope amid the ongoing invasion from Russia. Since the war began, shipments of grain out of Ukraine, considered one of the breadbaskets of the world, have all but stalled -- leading experts to fear a possible food shortage that could plunge millions into malnutrition.

Preparations and planning for ships that can export grain and similar foodstuffs from the three ports in Ukraine are still continuing, according to the JCC, which described the feat as a "historical" humanitarian mission. The initial run to move significant volumes of commercial grain is expected to last 120 days.

"The JCC 's work is critical to implement the Black Sea Grain Initiative that helps address global food security," the statement read. "The Initiative is focused on exporting grain, other foodstuffs and fertilizers, including ammonia, from Ukraine."

-ABC News’ Engin Bas

U.S. Secretary of State Antony Blinken on Monday condemned the conduct of Russian troops around the Zaporizhia power plant -- the biggest nuclear power plant in Ukraine and Europe -- calling it “the height of irresponsibility."

Speaking after nuclear nonproliferation talks at the United Nations in New York, Blinken said Russia was turning the power plant into a “nuclear shield."

“Russia is now using the plant as a military base to fire at Ukrainians, knowing that they can’t and won’t shoot back because they might accidentally strike a nuclear reactor or highly radioactive waste in storage,” Blinken said.

The secretary added that Russia's actions bring “the notion of having a human shield to an entirely different and horrific level.”

Russia was already accused of firing shells dangerously close to the Zaporizhzhia nuclear power plant in March as Russian troops occupied the facility in the first weeks of the invasion of Ukraine.

Russian President Vladimir Putin said on Monday a nuclear war should “never be unleashed,” according to local media. Putin stressed that Russia continues to fulfill its obligations under the Treaty on the Non-Proliferation of Nuclear Weapons, as well as its bilateral agreements with the U.S. on the reduction of nuclear weapons.

-ABC News' Edward Szekeres, Yulia Drozd, Max Uzol and Fidel Pavlenko

The United States is sending a 17th round of aid to Ukraine, consisting of more ammunition for HIMARS rocket systems and howitzers, White House spokesman John Kirby announced.

This aid comes from presidential drawdown authority, separate from any aid passed by Congress.

This package totals $550 million and brings the total of U.S. presidential drawdown aid given to Ukraine since February to $8.8 billion.

-ABC News’ Luis Martinez and Sarah Kolinovsky