Biden warns that the world will hold Russia accountable as Putin declared war on Ukraine.

Explosions were reportedly heard in Rivne Oblast overnight on Aug. 21 as Russia launched bombers and drones, prompting an air raid alert to be issued across all of Ukraine.

The attack allegedly hit the Novoshakhtinsk oil refinery, which has previously been targeted in Ukrainian drone strikes.

The plan would require countries that have signed security agreements with Ukraine to deliberate and respond quickly in the event of another Russian attack following a peace agreement. It would not include NATO membership for Ukraine.

Ukraine's Crimean peninsula, illegally occupied by Russia since 2014, is roughly 26 times smaller than Texas.

Closer to Ukraine, Lithuania said it was ready to put troops on the ground as part of a peacekeeping force, while Poland said its soldiers would assist the "coalition of the willing" from Poland.

In a joint statement, representatives of five Security Council members — Denmark, France, Greece, the United Kingdom and Slovenia — along with incoming member Latvia, denounced Russia's invasion of Georgia 17 years ago and its continued military presence in the country's Abkhazia and South Ossetia regions.

Poland's Deputy Prime Minister and Defense Minister Wladyslaw Kosiniak-Kamysz confirmed that the object, which fell into a cornfield near the village of Osiny, was a Russian unmanned aerial vehicle.

The Kyiv Independent spent a day with the 20th Separate UAV Regiment, also known as K-2, which specializes in ground robots, in northern Donetsk Oblast. We also spoke with the regiment's commander, Kyrylo Veres, about how these machines could shape the next phase of warfare in Ukraine, helping to reduce the risk to soldiers amid a growing manpower shortage.

Ukrposhta, Ukraine's state-owned postal service, is closing its offices in the front-line city of Kostiantynivka in Donetsk Oblast due to the deteriorating security situation, company CEO Ihor Smelyansky announced on Aug. 20.

"Valerii Zaluzhnyi has stated his position more than once, and as far as I know, it has not changed: while the war continues, we need to work to preserve the country, not think about elections," Zaluzhnyi's aide Oksana Torop said.