The European Union has opened two "specification proceedings" on Apple under the bloc's Digital Markets Act (DMA) that will see it instructing the iPhone

EU antitrust regulators launched proceedings on Thursday to ensure that Apple complies with landmark rules requiring it to open up its closed ecosystem to rivals or risk a possible hefty fine.

The European Union's enforcement arm said Thursday it's initiating a pair of "specification proceedings" into whether Apple is complying with its "interoperability obligations" under the Digital Markets Act.

The first focus of the DMA compliance initiative announced today is iOS. In particular, the EU will scrutinize a set of iOS features that consumers use to link their iPhones with connected devices. Officials will inform Apple how to implement those features in a DMA-compliant manner.

The European Commission plans to come up with its own measures that Apple has to follow to ensure interoperability if it doesn't want to pay huge fines.

Apple just received a very clear message that it still has a lot to do if it hopes to comply with Europe's new digital antitrust rules. Why it matters: The tech giant, which has built its entire business around its own closed-world ecosystem,