Border tensions escalate as Ukraine artillery fire kills four in Russian regions.

Four people were killed in two separate Ukrainian shelling attacks on towns near the border, according to the governor of Russia's Belgorod region. Officials in nearby regions also reported overnight drone attacks. Russia has reported intensified attacks from northern Ukraine, while Ukraine denies its military involvement and says they are conducted by Russian volunteer fighters. Russia has mounted around 20 separate missile and drone strikes against cities since the start of May.