Almost a million people in southern Colombia have been cut off from the rest of the country by a massive landslide, President Gustavo Petro said late on Thursday.

Some 700 people were evacuated by authorities from the southwestern municipality of Rosas before the landslide struck between Monday and Tuesday.

No deaths or injuries were reported but the main road linking the center and south of the country -- which also links Colombia to its southern neighbor Ecuador -- has been completely blocked, the president said.

Petro said heavy goods vehicles would not be able to access the south of the country for the better part of a month, and ordered emergency measures including an air bridge to ensure food can be delivered.

"The only paved road" between Colombia's south and center "has been destroyed," said Petro during a visit to the mountainous area.

The Via Panamericana highway "is the most important" road in Colombia, added Petro. "It connects (us) to South America."

The road closure means freight vehicles and cars have been forced to use an alternative route known as "the trampoline of death" due to its narrow roads and sheer drops on one side.

Though Colombia is currently in its wet season, the South American country has been experiencing unusually heavy and sustained rainfall since the end of last year.