NATO produced satellite photos which proved Russian artillery and armoured columns are now operating on Ukrainian soil on Thursday. Russia denies intervening in Ukraine by arming separatist rebels or sending soldiers across the border into the cities of Donetsk and Luhansk. Al Jazeera's Simon McGregor-Wood reports. Subscribe to our channel http://bit.ly/AJSubscribe Follow us on Twitter https://twitter.com/AJEnglish Find us on Facebook https://www.facebook.com/aljazeera Check our website http://www.aljazeera.com/