Two Elon Musk-backed businesses have officially sued Apple and OpenAI, accusing them of joining forces illegally to block threats from potential competitors, BBC reported.

The lawsuit, filed in the US by X and xAI, takes aim at Apple's decision to integrate OpenAI's chatbot into the operating systems of its smartphones, an exclusive arrangement that it says violated competition law.

The filing makes good on a threat Musk had lobbed against the two tech giants earlier this month, when he alleged that Apple favoured OpenAI in its app store rankings, according to BBC.

Apple did not immediately respond to a request for comment, while OpenAI said the filing was "consistent with Mr Musk's ongoing pattern of harassment".