Television viewers have said new thriller McMafia was troubled by “tiny” subtitles that made it difficult to follow the action.

The BBC series – which sees James Norton starring as the son of a Russian ex-mobster who is dragged back into his family’s shady past – got under way on BBC on Monday night.

Some viewers said they struggled with the subtitles used when the characters were speaking Russian, complaining there were too many and that they were too small.

One person posted on Twitter: “Oh @BBCOne the #subtitles on #McMafia are dreadful, too small and at times the letters disappear into the background.”

“Too many small subtitles @BBCOne This is not good #McMafia,” grumbled another.

One person said: “Watching #McMafia with my mum who is losing thread of programme as subtitles revert to tiny from her usual settings when character speaks in Russian. Such a shame @BBCOne Why no uniformity throughout for visually impaired?”

Another said it had a “huge amount of subtitles that were blurry at best & unreadable (white text on white background) at worst”.

“I wonder if anything can be done about the Russian subtitles being teeny for those who’d struggle to see them. Is there a way to fix it?” asked another viewer.

The show itself received mixed reactions.

Some praised the acting and said the series showed promise.

“Intriguing first episode! I think this will be as good as we hoped,” said one while another viewer said the cast deserved a standing ovation.

However, others said it was too slow and joked it should have been called “McDull” or “McSnooze”.

“What a disappointment #McMafia is. Even the brilliant James Norton can’t keep me watching. Switched off ,” said one disgruntled viewer.

McMafia continues on BBC1 on Tuesday.