Blasts were heard in Ukraine's capital Kyiv and major city of Kharkiv on Monday morning, the fifth day of Russia's military operations in the country, according to Ukraine's State Service of Special Communications and Information Protection.

Kyiv had been quiet for a few hours prior to that, it said in a brief statement on the Telegram messaging app.

The Ukrainian capital is still under a prolonged curfew that lasts from 5 p.m. until 8 a.m.