Rwanda has deployed what it called a “protection force” to the Central African Republic after its peacekeepers there were attacked by rebels advancing to the capital, Bangui.
The Rwandan and CAR governments have accused Former President François Bozizé of backing the rebels and plotting a coup, which he has denied.
UN peacekeepers have said the rebel advance has been halted.
Bozize has been barred from a presidential election due on Sunday.
Russia has also sent “several hundred soldiers and heavy weapons” to the country to support the government, the AFP news agency quotes a CAR government spokesman as saying.
Minusca forces have also been deployed beyond Bangui “to block armed elements”, AFP quotes a spokesman as saying.
President Faustin Archange Touadéra has insisted Sunday’s election will go ahead, saying the presence of the army and UN peacekeepers means people have nothing to fear.
But opposition parties, including that of Bozizé, have called for the vote to be postponed “until the re-establishment of peace and security”.
Rebel groups have seized several towns close to CAR’s capital, clashing with government forces and looting property, and the UN said its troops were working to prevent a blockade of Bangui.
Guenebem told AFP: “We categorically deny that Bozizé is at the origin of anything.”
The CAR is one of Africa’s poorest and most unstable countries, even though it is rich in resources like diamonds and uranium. The UN estimates that half of the population are dependent on humanitarian assistance and up to a fifth have been displaced.