Thousands of rural farmers, victims and students marched in cities across Colombia on Wednesday to demand a peace deal between the government and leftist rebels not be scuttled.

It's the second time in a week that Colombians are taking to the streets to support the accord signed with the Revolutionary Armed Forces of Colombia.

In Bogota, victims of the decades-long conflict carrying signs of dead loved ones were greeted by well-wishers handing white flowers symbolizing peace.

President Juan Manuel Santos is in talks with the opposition and FARC to save the accord after it was narrowly rejected in a referendum.

While a ceasefire remains in place the outlook for a deal is bleak with the FARC insisting the agreement is final and opponents pushing for conditions unacceptable to the rebels.