Mozambique's Frelimo-led government and the main opposition party, Renamo, resumed stalled talks on Monday, amid deepening military tensions between the two sides.

Meeting for the first time in three months, the former civil-war foes agreed on some rules for future talks, a small step forward, but a significant one amid continued violence.

Scores have died in skirmishes between Renamo militia and government forces since Renamo's leader, Afonso Dhlakama returned to a former civil war bush camp in October 2012.

He has vowed to return the country to war unless the government agree to discuss a list of demands, inlcuding the sharing of resource wealth.

A series of political talks aimed at ending the conflict broke down after government forces attacked Dhlakama's Gorongosa stronghold last October, sending him into hiding.

But on Monday the two sides returned to the negotiating table, agreeing to allow observers to take part in future talks.

"The question of the participation of third parties and the question of the participation of observers were agreed by the two sides," the deputy head of the government's negotiating team, Transport Minister, Gabriel Muthisse told state-run Radio Mozambique.

Renamo had called for foreign observers to be present.

"We have taken a step forward but... we wish to work towards agreeing on a code of conduct... and determining the people and entities who will take part in this process," Renamo's chief negotiator, Saimone Macuiane said.