At least three British citizens were among those killed in the earthquake in central Italy, an official from the town of Amatrice has told the BBC.
It comes after the UK government said it had offered help with the recovery effort following Wednesday’s quake, which killed at least 250 people.
Amatrice is one of the worst affected areas, along with the towns of Arquata, Accumoli and Pescara del Tronto.
The Foreign Office has not confirmed the deaths of the British nationals.
The 6.2-magnitude quake hit at 03:36 (02:36 BST), 100km (65 miles) north-east of Rome in mountainous central Italy.
About 5,000 rescue workers are combing through rubble for survivors using heavy machinery or bare hands.
UK Foreign Secretary Boris Johnson said additional staff had been deployed to the region to provide consular support.
He added: “My deepest sympathies are with the Italian people and everyone affected by the terrible earthquake that struck central Italy.
“The British government has offered any assistance that we can to help with the recovery effort and I have spoken with Italian foreign minister Paolo Gentiloni to express my condolences personally.”
Hundreds of aftershocks have rocked devastated areas of central Italy, hampering search efforts following the earthquake.
A strong tremor with magnitude 4.3 struck on Thursday afternoon, sending rescuers fleeing from already fragile buildings.
Firefighters and rescue crews using sniffer dogs have been working in teams around the hardest-hit areas of the country.
“We will work relentlessly until the last person is found, and make sure no one is trapped,” said Lorenzo Botti, a rescue team spokesman.
The towns are usually sparsely populated but numbers staying there have been swelled by tourists visiting for summer, making it difficult to estimate the precise number missing.
Little is currently known about the nationalities of those caught up in the quake, but Romania’s foreign ministry says that five Romanians have died and 11 are missing, while Spain’s foreign ministry says at least one Spaniard has died.