Belgian customs officers arrested 45 people on Wednesday as part of the country's biggest operation into cigarette counterfeiting.

The country has become a hub for cigarette trafficking to neighbouring countries.

Officers arrested 17 people of Ukrainian and Bulgarian nationality during a pre-dawn raid on a sweatshop in an industrial area of Aartselaar, near the northern city of Antwerp.

The men were housed in a dilapidated dormitory in the warehouse, working in shifts to dry tobacco and run it through rolling machines.

"This warehouse operates 24 hours a day, and the workers don't leave it, so as not to give any sign of suspicious activity to the neighbourhood," Florence Angelici, spokeswoman for the Belgian finance ministry, explained.

"And so they will sleep, work, eat, shower on site, without going out for weeks, even months," she added.

A large stock of cigarettes was ready to leave for the UK, in imitation branded packs with the health warnings that are common in the country.