France is "extremely worried about the announcement of the arrest of Sarath Fonseka and his aides a few days after the vote," a foreign ministry statement said.
"It also deplores the growing pressures to which journalists in Sri Lanka have been subjected in recent months," it said.
Fonseka, who was also Sri Lanka's former army chief, was arrested Monday and is to be court-martialled on charges of conspiring against the government, officials said.
Fonseka, 59, the only four-star general in the army, quit in November after falling out with his commander-in-chief, President Mahinda Rajapakse, whom he later challenged in January presidential elections.
Shortly after the poll, which Rajapakse won comfortably, the government accused Fonseka of plotting a coup to overthrow the president and assassinate his family members. International rights groups have criticised the Sri Lankan government for a clampdown on opponents and the media after last week's election and condemned the detention of su