The algae outbreak that threatened the Olympic sailing competition in Qingdao has spread hundreds of kilometres up the coast to popular tourist areas, even as Chinese officials on Friday claimed near-victory over the thick green sludge.

The long stretch of beach at Baishatan, 150km north of Qingdao, has been lined in recent days with 10-metre-wide slicks of algae that gave out a noxious odour to the few tourists who braved the sand, causing panic among tourist operators.