President Juan Manuel Santos said Monday that his government has opened "exploratory talks" with Colombia's main rebel groups in a bid to end a stubborn half-century-old conflict.

Santos' announcement in a brief televised address followed mounting rumours of talks supposedly held in Cuba between representatives of his government and the leftist Revolutionary Armed Forces of Colombia.

Santos offered no details of the talks, including when they began.

"In the coming days the results of the conversations with the FARC will become known," he said.

Santos said military operations would continue "on every single centimetre of national territory" during whatever peace process might emerge.

That statement was a clear allusion to the last peace dialogue held with the FARC, when the government surrendered a Switzerland-sized swath of southern Colombia to the rebels from 1990-2002 and reconciliation efforts collapsed as the guerrillas continued to mount attacks on security forces, kidnap politicians and traffic in cocaine.

Santos also mentioned that Colombia's No. 2 rebel band, the National Liberation Army known by its Spanish-language initials ELN had expressed a desire to participate in peace talks.

The ELN has also held failed peace talks with the government in the past.