The race to find survivors of the twin earthquakes that struck Venezuela entered a critical phase on Saturday, with the death toll rising to at least 920 and more than 51,000 people reported missing, as authorities restricted access to the worst-hit state of La Guaira to facilitate rescue operations.

The devastating 7.2 and 7.5-magnitude earthquakes struck on Wednesday, flattening homes and apartment buildings across parts of northern Venezuela. Aid agencies say the first 48 to 72 hours after a disaster are crucial for rescuing survivors trapped beneath rubble.

Officials announced late on Friday that entry into La Guaira, the epicentre of the destruction, would require official permits after traffic congestion and overcrowding began hampering rescue efforts.

Many residents have undertaken search operations themselves, citing a shortage of government rescue personnel in the hardest-hit areas. Neighbours armed with hammers, drills and power tools continued trying to reach those trapped beneath collapsed structures.

"Each person saved is a miracle," National Assembly President Jorge Rodríguez said. "We are not going to hide absolutely anything about the magnitude of this tragedy."

In La Guaira, Nazareth Jimenez watched neighbours struggle to cut through concrete slabs in search of her siblings, nephews, nieces and friends trapped beneath a collapsed building.

"My God, how are we going to get them out of there?" she said, appealing for heavy machinery from the Venezuelan government and the international community.

"There are still people alive in there," she added.

Acting President Delcy Rodríguez said the government was mounting a full-scale response during what she described as the "critical hours" for saving lives. She welcomed the arrival of international rescue teams and humanitarian assistance, adding that La Guaira had been militarised and additional personnel were being deployed.

Residents, however, said the assistance reaching affected areas remained insufficient.

The disaster presents a major challenge for Rodríguez, who assumed office in January following the removal of former President Nicolás Maduro. Venezuela continues to grapple with prolonged economic difficulties, complicating relief efforts.

Authorities said more than 3,300 people had been injured and 243 rescued as of Friday afternoon. Officials cautioned that the death toll was expected to rise, while the number of missing could include people who remain out of contact because of disrupted mobile networks or duplicate reports.

The International Organization for Migration estimated that up to 6.76 million people could be affected by the disaster, including around 2 million residents of Caracas. Experts said the destruction was worsened by the shallow depth of the earthquakes and their rapid succession.

Loyce Pace, the International Red Cross' regional director for the Americas, said many people remained afraid to return to damaged buildings.

"People are still terrified to reenter what were their homes," she said.

Thousands continued spending nights outdoors.

Omar Reyes, who said around 20 members of his family had died, searched through the rubble where two of his children remained buried.

"I've been left alone in this life," he said.

In Maiquetia, long queues formed outside shops and pharmacies operating with limited access. Some incidents of looting and disorder were reported in affected areas, with soldiers intervening to maintain order.

Search operations were also disrupted by heavy traffic and large numbers of motorcyclists, prompting rescue workers to repeatedly call for silence so they could listen for signs of life beneath collapsed buildings.

Nearby, Yuleidy Cadenas waited outside the remains of a collapsed public housing block, hoping her son, mother and brother would be found alive.

"I got on top of the rubble and told them to yell back, and nobody did, not my brother, nor my son or my mother," she said.

Venezuelan authorities said 861 rescue personnel and volunteers from Mexico, the United States, El Salvador, Switzerland, Colombia and other countries had arrived in the country, with additional teams expected.

Rodríguez said she had spoken with US President Donald Trump and Secretary of State Marco Rubio, who reaffirmed Washington's commitment to sending rescue teams and emergency equipment.