"Moscow acts on the assumption that a change of power by force is unacceptable. As is known, this is also the position of the international community, including the African Union. Such anti-constitutional actions deserve condemnation," the Foreign Ministry said.
It said Russia hoped the country's new leadership, which has pledged to hold democratic presidential elections, would honor its pledge and give the Mauritanian people "an opportunity to continue stable development within the bounds of the Constitution and in the interest of all sections of Mauritanian society."
A group of renegade army officers staged a coup in the early hours of Wednesday morning, detaining President Sidi Ould Cheikh Abdallahi and Prime Minister Yahya Ould Ahmed Waghf.
The leaders, along with other top government members, were arrested as soldiers took control of the capital and state radio and television was shut down.
Abdallahi became Mauritania's first democratically elected president when a military junta handed power back to a civilian government through elections in 2007 after a bloodless coup in 2005.
The president threatened last month to dissolve parliament after lawmakers filed a motion of no confidence in his new government, which then resigned.
The largely desert country has had a history of coups since its independence from France in 1960.
The European Union on Wednesday condemned the coup, demanded that the president be returned to power, and threatened to halt aid to Mauritania.