Armed robbers stole jewellery worth millions of euros as they attacked two security vans travelling on a French highway overnight, in an operation described as "spectacular" by the local press.

Police said about 15 masked men armed with automatic weapons assaulted the vehicles at a tollbooth of the A6 highway connecting Paris and Lyon near the commune of Avallon, about 200km southeast of the capital.

They forced the drivers out at gunpoint and hijacked the vans, which were later found abandoned nearby, robbed of their precious cargo - mainly jewels worth an estimated value of €9m (£6.3m, $9.5m).

No shots were fired during the attack that left no one injured. The attackers drove away in high-powered vehicles that are being sought after by police.

Security forces backed by helicopters were combing the Yonne region in Burgundy for traces of the robbers.