An emergency meeting of the UN Security Council has denounced Russia's recognition of two rebel-held areas of Ukraine as a 'pretext for war'.
Russian president Vladimir Putin announced last night that he was sending troops to the two breakaway regions.
He's described them as 'peacekeepers' - which western governments have called 'nonsense'.
Witnesses have spotted a number of tanks and personnel carriers near Donetsk.
Cormac Smyth - an advisor to Ukraine's former Foreign Minister - says the west needs to act in a strong and united way.
"They need absolute unity in the West. And they need sanctions but they need real sanctions.
"The sanctions in 2014 were probably on a scale of three out of 10. They need to be nine out of 10 or 10 out of 10. Russia now needs to be sanctioned back to the Stone Age.
"We hear an awful lot of talk about how severe sanctions are going to be. But we need to see the detail and we need to see Putin's feet held to the fire."
