LONDON (Reuters) - British Prime Minister Boris Johnson on Friday said he was cautious about rising cases of COVID in Europe, warning of gathering "storm clouds" of a new wave of coronavirus infections.

       Britain has had much higher rates of COVID-19 than the rest of Western Europe since the summer when Johnson scrapped coronavirus restrictions in England.

       However, rates in Britain are now coming down just as they are rising sharply in countries such as Germany, Austria and the Netherlands. Parts of Eastern Europe have also seen a sharp rise in cases.

       "I'm seeing the storm clouds gathering over parts of the European continent. And I've got to be absolutely frank with people: we've been here before. We remember what happens when the wave starts rolling in," Johnson said in a broadcast clip, referring to previous waves of infections.

       Johnson has said he aims to navigate winter without locking down the economy, having done so three times previously in response to rising cases. He is instead relying on COVID booster shots for the elderly and vulnerable.

       The prevalence of infection in England is now dropping from its highest levels of the year according to Office for National Statistics estimates.

       But Johnson said that unless people came forward for boosters, cases might rise again.

       "We've got some encouraging numbers in the sense that they've been drifting down for a while, but it's not clear that that drift is going to continue," Johnson said.

       "I'm looking at what's happening overseas, and I'm simply saying to the British people... This is the moment to get your booster."

       (Reporting by Alistair Smout; editing by Michael Holden)