"The slowing of growth in China since the beginning of 2015 has reduced euro area exports, in particular exports of machinery and transport equipment. This has had adverse repercussions, in particular, for exporters of manufactured goods, which account for almost 90 percent of goods exports to China," the bank said in Wednesday's "financial stability review."
The ECB, which controls monetary policy in the 19 countries that use the euro, said that a 1 percentage point slowdown in Chinese real gross domestic product (GDP) would knock around 0.1-0.15 percentage points off euro area activity after two to three years.
An economic "confidence shock" — perhaps due to a worse-than-expected slowdown in China — could lead to a tightening of financial conditions in emerging markets and a "further slowdown of euro area foreign demand," the ECB said.
"Moreover, capital outflows from China, if not counterbalanced by other private or official flows, could trigger a depreciation of the Chinese currency and, in its wake, exchange rate depreciations of other emerging market currencies," it added.
The bank said that China's huge economy meant it had wielded a "significant effect" on the price of oil, but that this had waned in recent years as its rapid growth slowed.