<span style="color: #222222;">NATO Secretary General Jens Stoltenberg urged Moscow again on Wednesday to prove that it is pulling back troops amid tensions over a military build-up on Ukraine's borders, saying soldiers and tanks often move about.<br />''<br />''It remains to be seen whether there is a Russian withdrawal but, what NATO sees is that they have increased the number of troops, and more troops are on the way. Stoltenberg told reporters at the start of a two-day meeting of NATO defence ministers at the alliance's headquarters in Brussels.<br />''<br />''If they really start to withdraw forces, that's something that will be welcomed. They have always moved forces back and forth so just that movement of forces, of battle tanks, doesn't confirm a real withdrawal.</span><br />