The head of the International Atomic Energy Agency (IAEA) said on Tuesday that the agency will step up assistance to Ukraine to protect the country's energy infrastructure, which is vital to the safety of its nuclear power plants (NPPs).

IAEA Director-General Rafael Grossi announced the move in a statement after meeting with Ukrainian President Volodymyr Zelenskyy in Kyiv earlier in the day.

The move followed "a number of missile attacks that have either directly caused the disconnection of several nuclear power reactors, or led to dangerous instability of the national grid," according to the statement.

The United Nations nuclear watchdog will soon dispatch an expert team to some of the damaged Ukrainian sub-stations, "electrical switchyards forming the backbone of the grid," and assess the situation there, the statement read.

"The safety of operating nuclear power plants is dependent on a stable and reliable connection to the electricity grid," Grossi said. "The situation is becoming increasingly vulnerable and potentially even dangerous in this regard."

According to the statement, strikes on Ukraine's energy infrastructure on August 26 "caused major fluctuations in the power supply and led to the temporary shutdown or disconnection of reactor units at the Rivne and South Ukraine NPPs, one of which has still not returned to full operation."

Grossi will also travel to Zaporizhzhia NPP, one of the largest NPPs in Europe, later this week to assess the nuclear safety situation there, the statement said.

The IAEA currently has expert teams stationed at all of Ukraine's NPPs to help maintain nuclear safety and security, according to the agency.