The European Commission raised competition concerns over MMG's (HKG:1208) proposed acquisition of Anglo American's nickel business, according to a statement on Wednesday.
The Commission said the deal may restrict competition in the low-carbon ferronickel market.
It said MMG could divert low-carbon ferronickel supply from European markets to affiliated stainless steel producers controlled by China's SASAC, potentially raising costs for European stainless steel producers.
The Commission said the market is highly concentrated and alternative supply sources for European customers are limited.
MMG and Anglo American did not immediately respond to' request for comment.