Ukrainian forces have massed tanks and armored vehicles around 20 kilometers (12 miles) south of the rebel-held city of Donetsk, Agence France Presse journalists said Thursday.

A column of vehicles stretching a kilometer and a half (one mile) arrived on Wednesday without facing any resistance, Ukrainian soldiers said, as part of a campaign to surround Donetsk and the neighboring city of Lugansk, also controlled by pro-Russian separatists.