French police say they have dismantled a gang of thieves believed to have stolen €1m (£830,000) worth of grands crus wines from prestigious Bordeaux vineyards.

About 300 gendarmes, mobilised across four regions of south-west France and Paris, arrested 20 suspects on Monday after a series of raids. Detectives believe the gang, which they described as "very organised and professional", carried out a series of thefts between June 2013 and last week and were stealing the wines to order.

Colonel Ghislain Réty, gendarmerie commander, said: "It was a highly organised group. In each case they would steal a van and then head to the vineyards they had already chosen and load up several dozen cases of wine."

After removing the cases from the designated chateau's stores and escaping, the thieves cleaned their fingerprints from the vehicle with bleach and then set fire to it. The last theft took place on 5 February, Réty said.

Detectives will not say how they managed to break into so many vineyards and the winemakers – concerned about their reputations and security – have also remained discreet. Investigators say the thieves were very well informed and that the thefts were carried out in a matter of minutes.

In total, 13 chateaux and two wine depots where bottles from several chateaux were stocked, were targeted. The thefts began in March last year.

The co-ordinated raids, as part of what was labelled Operation Cassevin, began at 6am on Monday. Five men, aged 18 to 55, were said to be the brains of the network and are accused of carrying out the thefts.

They, along with 15 others who were reportedly part of two teams that distributed the wines, are being held in custody. Police say they found hundreds of bottles of wine and tens of thousands of euros in cash, as well as stolen vehicles and weapons during Monday's raids. "We are still looking into how the merchandise was supposed to be sold," Réty said.

The arrests will come as a relief to the wine chateaux of Bordeaux, where a theft has been reported roughly every 15 days for the last six months. The 13 vineyards that were victims of theft have not been named by police – wine producers are nervous about the possibility of information about the thefts being used to produce fake bottles.

Bernard Farges, president of the Bordeaux wine producers' association, the CIVB, said the arrests were "reassuring". He said thieves were targeting the grands crus because they were "valuable products" that could easily be sold on.

Last June, gendarmes broke up a separate network of thieves who had stolen some 500 bottles worth €300,000 including of wine from the top chateaux of Yquem, Petrus, Ausone and Cheval Blanc worth €700-€1,000 each.