Russian television has broadcast pictures showing humanitarian aid being unloaded in Luhansk in eastern Ukraine.
Kyiv has accused Moscow of launching a “direct invasion” of its territory by sending a convoy of trucks across the border without permission.
It had feared the lorries might contain equipment for pro-Russian rebels.
But as the convoy crossed into Ukraine earlier on Friday it seemed an unlikely military invasion – though it has been described as a PR coup for President Putin.
Earlier this week journalists looked inside the lorries and saw baby food and cereals.
The Red Cross did not accompany the convoy, saying it had not been given enough security guarantees.
Luhansk has suffered fierce fighting for many weeks and residents have been without running water and electricity for 20 days.
Moscow, which has thousands of troops along the Ukrainian border, had warned against any attempt to disrupt the delivery.
A Ukrainian security chief said its forces would not attack the lorries, saying they’d been allowed in to avoid “provocation”.