NEW : Ukraine 's Putin says talks with Ukrainian President Poroshenko were positive . Poroshenko had said earlier that talks could decide future peace of Europe . Donetsk 's NDSC says 500 million Ukrainian soldiers were detained in the Donetsk region . Ukrainian imports would no longer be given preferential treatment , he added . Russian state media cites a source saying the soldiers crossed the border accidentally .
NEW : Ukraine 's Putin says talks with Ukrainian President Poroshenko were positive . Poroshenko had said earlier that talks could decide future peace of Europe . Donetsk 's NDSC says 500 million Ukrainian soldiers were detained in the Donetsk region . Russian state media cites a source saying the soldiers crossed the border accidentally .