Two French journalists known for their critical writings about Moroccan King Mohammed VI have been arrested in France for allegedly trying to blackmail the monarch, according the Paris prosecutor's office and the king's lawyer.

The prosecutor's office said on Friday the two reporters, Eric Laurent and Catherine Graciet, remained in detention. Their lawyers have not spoken publicly about the matter.

Eric Dupont-Moretti, a lawyer for the king, had told RTL radio on Thursday that Laurent claimed he and Graciet were writing a compromising book about the monarch and demanded $3.4m to keep it unpublished.

Dupont-Moretti said the Moroccan leadership filed a lawsuit in Paris and the arrests came after a sting operation.

Moroccan website Le360.ma, which has close ties to the palace, reported details of how Laurent allegedly approached the palace demanding money.

Moroccan representatives held two more meetings with the journalists, that were monitored by police, and they were arrested after leaving a restaurant with money that was allegedly a down payment, the report said.

The king is seen abroad as a force for stability in the region and has been lauded for pursuing democratic reforms and pushing women's rights in the North African country.

Critics, however, say that he rules behind a democratic facade and presides over a corrupt economy dominated by his associates.

Much of these critiques were summarised in Laurent and Graciet's 2012 book "Predator King," which was banned in Morocco and detailed how the king's fortune allegedly ballooned after he took the throne in 1999.

Source: AP