The competition authority said in a statement it decided to launch a deep investigation because "there are strong indications ... that it (the deal) could result in significant obstacles to competition in various markets."

It said those markets included television content production, advertising and telecommunications. Altice, which owns Portugal's largest telecom operator MEO, agreed to buy Media Capital in July last year from Spain's Prisa in a 440 million euro (390.38 million pounds) deal.

(Reporting By Axel Bugge, editing by Andrei Khalip)