Russian troops have been surrendering en masse — even escaping the Luhansk region in stolen cars and bicycles, with some replacing their uniforms with stolen civilian clothes, according to a spokesperson for Ukrainian military intelligence.

"They understand the hopelessness of their situation," the spokesperson said.

More than 20 towns and villages have been freed in 24 hours as the Russian military and its local collaborators flee, the spokesperson said.

Russian troops are allegedly making attempts to contact Ukrainian officers in an effort to independently negotiate the surrender of their units, as long as they get assurance of being treated according to the Geneva Conventions, according to the Ukrainian military spokesperson.

So many have surrendered that the country is running out of space to accommodate Russian prisoners of war, a Ukrainian presidential adviser said on Monday.

-ABC News' Tomek Rolski

The International Atomic Energy Agency has established a presence at the site of the nuclear power plant in the southeastern Ukrainian city of Zaporizhzhia due to continued shelling in the region, IAEA Director General Rafael Mariano Grossi said in a statement Monday.

The mission, intended to ensure nuclear safety and security and to allow inspectors to take vital safeguard activities, has made clear of the "urgent and imperative goal" to halt the bombing and establish a protection zone surrounding the power plant, which is the largest in Europe.

In addition to the protection zone, the IAEA has established a second safety pillar that states all safety and security systems should be fully functioning and operating "normally and unhindered." During observations, the safety team observed military equipment and vehicles getting in the way of systems functioning optimally, Grossi said.

The third pillar of the safety plan states that operating staff must be able to perform their duties without undue pressure or duress -- an issue that has been raised many times since the Russian occupation of Zaporizhzhia began in March, according to the statement.

The IAEA is also mandating the maintenance of constant off-site power supply so that the power plant does not lose crucial functionalities, including the cooling of reactors and spent fuel, as well as uninterrupted supply chains and transportation to and from the site, which will be "especially crucial" should backup generators be needed again.

Effective radiation monitoring systems -- both on and off site -- and emergency preparedness, as well as continued reliable communication with the regulator and others, were also safety pillars outlined in the plan.

"Despite the ongoing challenges of the war, we have continued to implement safeguards in Ukraine," Grossi said.

-ABC News' Joe Simonetti

U.S. Secretary of State Antony Blinken stopped in a war-torn section of Irpin in the Bucha district as part of his trip to Ukraine.

The city's deputy mayor, Dmytro Nehresha, showed Blinken ruined buildings and streets still littered with debris from Russian strikes in the early weeks of the war.

The Russians have indiscriminately shelled this city. Nehresha described how young and vibrant the city once was.

Irpin was under Russian control for nearly a month before Ukraine won it back, he explained.

Khrystyna Podyryaka, the director of the War Crimes Investigation Unit for the national Ukraine Police, was also present for the stop. She told Blinken that the unit is investigating 30,000 war crimes, two-third of which directly involve civilians.

"There has to be accountability for those who committed atrocities," Blinken responded.

At one point, nearly all residents of Irpin had been evacuated. Despite the devastation, almost 80% have returned, Nehresha said.

The secretary expressed confidence that the city would be restored. Before Blinken departed, he was asked to sign an Irpin flag.

-ABC News' Shannon Crawford

U.S. Secretary of State Antony Blinken met with Ukrainian President Volodymyr Zelenskyy at the heavily fortified Presidential Administration Building in Kyiv.

The meeting took place in a gilded room darkened by blackout shades. Other windows in the building were covered by sandbags.

Blinken was joined by his deputy chief of staff, Thomas Sullivan; Under Secretary of State for Political Affairs Victoria Nuland; U.S. Ambassador to Ukraine Bridget Brink; and Assistant Secretary of State for European and Eurasian Affairs Karen Donfried. Zelenskyy was accompanied by his foreign minister, Dmytro Kuleba, Ukraine’s ambassador to the U.S., Oksana Marakova, and other top members of his cabinet.

In English, Zelenskyy thanked the U.S. for its "enormous" support, saying he appreciated the delegation’s visit. He also presented Blinken with a Ukrainian medal, "The Order of Prince Yaroslav the Wise," awarded for distinguished service to the country.

Blinken commended the bravery of the Ukrainian people and their success on the battlefield, noting the counteroffensive underway was proving "incredibly effective," calling it a "pivotal moment" that would put Kyiv on better footing for future negotiations.

“This is your homeland, not Russia’s,” he said. “It’s as basic as that.”

Blinken also spoke about the recent announcement of $2 billion in long-term aid for Ukraine and other countries in the region deemed to be at risk of facing Russian aggression, highlighting the “durable and enduring” commitment of the United States.

He noted how Russia was feeling the impact of economic sanctions, pointing to Moscow turning to Iran and North Korea for weapons as evidence.

Blinken last met with Zelenskyy in person in April, when he visited Kyiv.

-ABC News' Shannon Crawford