A landslide in Colombia's south-western border province of Putumayo has sent mud and debris crashing onto houses, killing 254 people and injuring hundreds more.

Key points:

• Rescue efforts are hampered by bad weather, partially blocked roads
• "There's nothing left — but thank God we have our lives," one resident says
• Colombian President Juan Manuel Santos has flown to Mocoa to oversee rescue efforts

Heavy rains caused several rivers to overflow, pushing sediment onto buildings and roads in the provincial capital of Mocoa.

Colombian President Juan Manuel Santos flew to Mocoa, which has a population of 345,000, to oversee rescue efforts on the city outskirts and speak with affected families.

He declared a state of public emergency in the region and expressed condolences to the victims.

"We will do everything possible to help them," Mr Santos said after confirming the death toll.

"It breaks my heart."

The army said in a statement that 254 people were killed, 400 people had been injured and 200 were missing.

More than 1,100 soldiers and police officers were called in to dig people out in 17 affected neighbourhoods.

A man who escaped with his wife and seven-month-old baby after a river overflowed said there was hardly any time to flee before the water came rushing in.

Eduardo Vargas was awoken by the sound of neighbours banging on his door and quickly fled with his family amid the sound of people crying in panic. They climbed up a small mountain to safety before their home destroyed.

 

Returning to the site late on Saturday, he said:

"There is nothing left — but thank God we have our lives."

Carlos Ivan Marquez, the head of the national disaster unit, said in a statement: "We have sent a team of 150 people to make our response effective and machinery began work immediately.

"We will be with the governor and the mayor giving all necessary attention."

Photos posted on Twitter by the air force showed neighbourhood streets filled with mud and damaged houses while cell phone videos on social media showed residents searching for survivors in the debris.

"It's a big area," Mocoa Mayor Jose Antonio Castro told Caracol.

"A big portion of the many houses were just taken by the avalanche but above all the people were warned with enough time and they were able to get out but houses in 17 neighbourhoods have basically been erased."

Two bridges also were destroyed, Mr Castro said.

Heavy rains and a mountainous landscape regularly cause landslides in the Andean country.