Russian forces appear to be stretched thin in Ukraine, giving Kyiv an opportunity for a surprise attack in the country's east.

Much of the fighting has been focused in the southern region of Kherson. Russian troops have been redeploying from other areas, including eastern Ukraine.

A US think tank says that Ukrainian forces have used the move as an opportunity. They've launched a counteroffensive and retaken some of their territory in the Kharkiv region.

Ukrainian President Volodymyr Zelenskyy says, "This week we have some good news from the Kharkiv region. You all have probably seen the reports about the activity of the Ukrainian defenders, and I think every citizen is proud of our soldiers. We should feel good about it."

Ukraine has also now claimed responsibility for last month's explosions at Russian military bases in Crimea.

The blasts destroyed a number of Russian military aircraft. Ukrainian officials have vowed to retake Crimea, which was annexed in 2014, and has recently served as an important staging area for Russia's invasion.

Meanwhile, Western nations in the UN Security Council have criticized Russia for its treatment of Ukrainian citizens in captured areas. They estimate that Russian troops have detained, interrogated and forcibly deported roughly one million Ukrainians.

An UN human rights senior official said they have verified that Russian forces subjected Ukrainian civilians to security checks and personal data collection.

The US Ambassador to the UN, Linda Thomas-Greenfield, says Moscow appears to be preparing for "an attempted annexation".

The ambassador also says, "These operations aim to identify individuals Russia deems insufficiently complaint or compatible to its control."

Russia's ambassador has dismissed the allegations, and accused Western countries of launching a disinformation campaign.