Tensions over disputed islands in the East China Sea have damaged Sino-Japanese trade relations and caused a dent in the automotive industry, the Asahi Shimbun reports.

The massive anti-Japanese protest that broke out in Beijing last month, leaving smashed Japanese-made police cars in its wake, may have been a sign that a slump will be likely. Nissan Motor Co Ltd.’s Chief Operating Officer Toshiyuki Shiga said that Japanese car makers saw a drop in sales, particularly in August. Nissan sales dropped from 98,100 vehicles in July to 95,200 last month. But an economic slowdown in the world’s second largest economy may have also reigned in demand.

Despite their wartime past and long-time rivalry for regional clout, China and Japan have deepened economic ties over the years which keeps trouble at bay. Two-way trade peaked 14.3% year on year in 2011 to $345 million.