International rescuers and aid groups rushed Tuesday to help victims of Ecuador's earthquake as searchers dug for families trapped in rubble three days after the disaster that killed more than 400 people.

Fears rose for thousands of people left homeless by Saturday's powerful 7.8-magnitude quake, prey to disease-bearing mosquitoes and dirty drinking water.

Hopes that more survivors would be found in the heaps of rubble and twisted metal that used to be homes, hotels and businesses waned at the crucial three-day point after the disaster.

But sniffer dogs and mechanical diggers were still busy at work in the wreckage of towns such as Pedernales and Manta on Ecuador's Pacific coast as the stench of rotting bodies filled the air.

Rescuers in Manta got a boost on Tuesday at dawn when they pulled a woman alive from the ruins of a shopping center.

Local media had earlier reported that a girl was rescued from the ruins of a building after being trapped for 20 hours in Pedernales.

Firefighting captain Freddy Arca pointed to the ruins of a hotel in Manta as drills and jackhammers rattled around him.

"We know that there is a man, his wife and their two-month-old baby in there. And there may be up to nine other people," he said.

UNICEF warned that 150,000 children were affected by the disaster.

It said landslides were complicating rescue efforts in some areas, and some towns were without electricity.

It was sending water-purifying tablets and mosquito nets to the zone to protect victims against the Zika virus and other diseases.

Oxfam said it was sending 2,000 kilograms (4,400 pounds) of material for providing safe drinking water.

- Aid airlifts -

The quake killed at least 413 people and injured more than 2,000, according to the latest government count.

Among the dead were six Colombians, two Canadians, one US national and a nun from Northern Ireland as well as other victims from Britain, Cuba and the Dominican Republic, the Ecuadoran foreign ministry said.

The United Nations refugee agency UNHCR said it would airlift supplies including hundreds of tents and kitchen sets.

It said it aimed to provide shelter and aid to 40,000 people, including Colombian refugees settled in the area.

The Spanish Red Cross estimated that up to 100,000 people would need assistance.

The World Bank said it had a credit line of $150 million ready to help with reconstruction. Correa's government said it had access to $600 million in emergency credit overall.

But Correa said rebuilding will cost up to $3 billion, in a television interview Tuesday.

Although Ecuador frequently suffers seismic shudders because of its position on the Pacific Rim's "Ring of Fire," the weekend's quake -- which lasted a full minute -- was the worst in nearly 40 years.

"I hope we will learn lessons for the future from this most painful experience," said Correa said.

"After the earthquake in Haiti (in 2010), people started considering much stricter rules for construction which came into force in 2014, but before that there were some really tremendously precarious buildings and that is perhaps why the damage is so great."

- Noises in the rubble -

In Manta, two young women with eyes red from crying wandered around near the ruined hotel.

"My brother Irvin is under there," says one, Samantha Herrera, 27. "The firefighters only arrived this morning. Ecuador is not prepared for such a catastrophe."

Rescuers said they could hear a noise from someone under the wreckage. Arca ordered the skinniest members of his team to wriggle into a gap in the rubble.

The man came back up looking pale. Searching for survivors, he found two dead bodies.

"But we can still hear the noise," Arca said.