ROME (Reuters) - At least 12 migrants died off the coast of Libya on Wednesday after they put to sea in stormy weather, the Italian coastguard said, adding that many others might have died in the incident.

Some 29 people were rescued when their rubber dinghy started to take in water 25 miles (40 km) north of Libya. An Italian navy helicopter took part in the rescue operation, helping ferry survivors to safety.

“The dinghy was put to sea despite very bad weather at the time,” said a coastguard spokesman in Italy.

Twelve bodies were recovered, but it was not clear how many people might have originally been on the boat and rescuers are continuing to sweep the area in search of other possible victims.

Human smugglers often cram as many as 100 migrants onto the unsafe dinghies before pushing them out to sea. Once the migrants reach international waters they call for help by satellite phone.

More than 3,740 migrant deaths have been recorded this year in the central Mediterranean, nearly matching the death toll recorded for all of 2015.

Over the first 10 months of the year, almost 155,000 migrants have reached Italy, most of them from sub-Saharan Africa. This is the same number as for all of last year, but down on the 170,000 arrivals registered in 2014.