Almost half of Ukraine will require mines to be cleared, as "even cups" can be packed with explosives, the country's State Emergency Services reported.

An area nearly 300,000 square kilometers, or slightly larger than the state of Texas, will require a careful sweep because of explosive materials left behind by the Russian military.

Some are regular munitions, grenades, and rockets abandoned by the retreating Russian forces. Others are deliberately placed explosives that range in the complexity of their detonation mechanisms.

"We are neutralizing anywhere from two to six thousand explosive materials every single day," according to Oleh Bondar, head of the Department of Pyrotechnic Works and Humanitarian Demining of the State Emergency Services.

The United Nations Office for the Coordination of Humanitarian Affairs stated that Ukraine is one of the most mine contaminated countries in the world.

"Even before the ongoing military offensive, over 1.8 million people were already living surrounded by mines for eight years," OCHA wrote on its Twitter page.

Bomb disposal teams are concentrating on public areas of recently liberated areas around Kyiv. In a televised address on Saturday, Kyiv regional officials warned that residents will be hearing explosions for the foreseeable future.

"There are mined houses, cars and even corpses that were left after the enemy's retreat," added the head of Kyiv's Military Regional Administration, Oleksandr Pavlyuk.

The mine detection and disposal also is occurring in the more active areas near Kharkiv, an eastern city that is under daily shelling; and Mykolaiv, a southern city.

In Kharkiv, emergency workers have uncovered small, delayed-action explosives.

"Do not touch these objects no matter what; don't approach them and do not try to get rid of them yourself," warned Kharkiv Gov. Oleh Synehubov.

In the northern Sumy region, more sinister seismic mines have been uncovered and reported by Human Rights Watch. The POM-3 "medallion" anti-personnel fragmentation mines are equipped with a seismic sensor that detects the sound of an approaching target. The mine's detonation can cause death and injury within a 50-foot radius.

These mines are banned under the International Mine Ban Treaty of 1997.

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