U.N. human rights chief Michelle Bachelet says her office has confirmed that 102 civilians, including 7 children, have been killed, and 304 others injured in violence in Ukraine since Thursday, as she cautioned that the tally was likely a vast undercount.

She cited updated U.N. figures that more than 420,000 people have fled the country in the last several days.

“Most of these civilians were killed by explosive weapons with a wide impact area, including shelling from heavy artillery and multi-launch rocket systems, and air strikes,” Bachelet told the Human Rights Council in Geneva on Monday. “The real figures are, I fear, considerably higher.”

The count by the office of the U.N. High Commissioner for Human Rights follows strict methodology and verification measures.

Bachelet said millions of people have been “forced to huddle in different forms of bomb shelters."

U.N. Secretary General Antonio Guterres told the council: “The escalation of military operations by the Russian Federation in Ukraine is leading to escalating human rights violations.”

The Kremlin has denied that the Russian military targeted populated areas in Ukraine despite abundant evidence that residential buildings, schools and hospitals have been hit during the Russian invasion.

Kremlin spokesman Dmitry Peskov alleged Monday that civilian casualties have resulted from members of right-wing Ukrainian nationalist groups using civilians as shields and putting military equipment in populated areas. Peskov’s claims couldn’t be independently confirmed and they contradicted statements from Ukrainian officials who accused Russia of targeting civilians.

Peskov did not comment on Russian demands in planned talks with Ukrainian officials, saying it’s necessary to allow negotiations to proceed before making public comment. He also declined to spell out Russian President Vladimir Putin’s order to put Russian nuclear forces on high alert.