France's worst drought on record this summer has sharpened debate over water resources in the European Union's biggest agricultural sector. Artificial reservoirs have been supported by some farmers as a way to use water efficiently, but have been decried by critics as outsized and favouring large farms.

Several thousand opponents defied a ban on protesting at the planned reservoir in the rural district of Sainte-Soline, with French television showing protestors roaming across fields towards the fenced-off construction area and being repelled by tear gas.

There were 61 injured, including 22 seriously, among the police who were attacked with fireworks and Molotov cocktails by some protestors, the local prefect said in a statement.

French Agriculture Minister Marc Fesneau condemned on Twitter the violence against police and criticised protestors for "the intention to block a project developed locally over years."

Green party officials who joined the protest blamed an excessive security presence that mobilised over 1,500 police.

"All that to protect a water grab in the midst of a drought," lawmaker Sandrine Rousseau tweeted.

Four protestors were injured and six arrested, the prefect said.