Along with Cuba, Chile and Venezuela, the other three countries facilitating peace talks between the two sides, Norway warned that the fighting was causing renewed suffering.
"We urge the parties to strictly restrict any actions that cause victims or suffering in Colombia, and to step up the implementation of confidence-building measures," Norway representative Idun Aarak Tvedt said in a statement read to journalists.
"We consider these steps to be essential in order to guarantee the conditions for and create a climate conducive to achieving agreement."
Cuba and Norway are acting as so-called "guarantor" countries in the talks that began in November 2012. Chile and Venezuela are acting as "escort" countries.
Rebel chief negotiator Ivan Marquez welcomed the appeal. He accused government forces of stepping up attacks on rebel camps while the guerrillas were observing a unilateral truce, which they finally ended in May after five months of relative calm.
The government side had no immediate public reaction to the appeal from the four countries trying to help the peace process.
The fresh violence followed relative calm after a unilateral ceasefire the Farc initiated in December.
Since then, about 30 rebels have been killed in army operations and recent surveys show the public to be wary about the peace process.
Colombia's civil strife dates back to 1964 and has drawn in left-wing guerrillas, right-wing paramilitaries and drug gangs at various times, killing more than 220,000 people and uprooting as many as six million.
Despite the renewed bloodshed, the Colombian government said for the first time Saturday that it was potentially open to a bilateral ceasefire.
As guarantors of the peace process, diplomats from Norway and Cuba attend all sessions of the peace talks, while escort countries Chile and Venezuela only go to the final session of any given round.
The four are not mediators per se. They do not participate in the talks, although they do speak separately to the Colombian government and the Farc.
So far, the two sides have agreed on three points of a six-point agenda for the peace process.