THABEIKKYIN, Myanmar (AFP) -- Myanmar rescuers struggled Monday to help villagers hit by an earthquake that aid agencies said killed at least 13, injured dozens and caused a bridge and mine to collapse.

A series of powerful aftershocks rattled nerves after Sunday's 6.8-magnitude quake, which sent terrified people running from homes and hotels in the country's second-biggest city of Mandalay and surrounding villages.

Authorities said they were providing help to victims, including those without shelter after more than one hundred homes were damaged, but that communication problems made it difficult to assess the scale of the destruction.

An AFP team in the town of Thabeikkyin saw significant damage in the area, which is near the epicentre of the earthquake and has been cut off from mobile phone contact.

Patients at the local hospital were being treated in tents outside amid fears buildings could be vulnerable to further tremors.

"We decided not to keep the people inside the hospital building as the quakes have been coming continuously," said a local official, asking not to be named.

He said three people from the area had died in the quake, including two children who drowned after the riverbank they were working on collapsed. It was unclear whether the deaths were included in official tallies.

Villagers in other settlements north of Mandalay told AFP earlier they had yet to see rescue teams following the quake.

"I have never felt such a big earthquake in my life. Everybody is terrified," said Win Tint, the head of Khu Lel village near Sint Ku township.

Some 40 buildings in the village were damaged and residents had been forced into temporary shelters set up in the fields. "The situation is quite bad. No rescue team has arrived here so far," he said.

Following the initial jolt, which was felt as far away as the Thai capital Bangkok, the US Geological Survey recorded two further strong quakes of 5.8 and 5.6-magnitude.

A United Nations Office for the Coordination of Humanitarian Affairs report Sunday said government departments had indicated "significant damage to houses, infrastructure and public buildings, including primary and secondary schools, monasteries and pagodas in various locations".

At least 100 homes were said to be damaged between Thabeikkyin and nearby Shwebo township, it said, adding the government's Relief and Resettlement Department had provided tents.

A situation report from Save the Children on Sunday put the number killed at 13, including four labourers who plunged into the Irrawaddy River near Sint Ku when the steel structure of a large, partially built bridge collapsed.

It said the other fatalities included six in Sint Ku township, two of whom died when a gold mine caved in.

An official from the relief and resettlement department on Sunday confirmed a death toll of seven, with four still considered missing from the bridge construction site.

The U.N.'s chief in Yangon, Ashok Nigam, said aid stocks were stretched, given the ongoing humanitarian crisis in Rakhine state in western Myanmar, where communal unrest has forced more than 110,000 people to flee their homes.

"We do have a very intense emergency going on in Rakhine and the stocks are low," he told AFP.

The quake came little more than a week before US President Barack Obama is due in Myanmar on a historic visit, as the West rolls back sanctions to reward dramatic reforms under a new regime that replaced outright army rule last year.

Earthquakes are relatively common in Myanmar. The USGS said six strong earthquakes, of 7.0-magnitude and more, struck between 1930 and 1956 near the Sagaing Fault which runs north to south through the centre of the country.

A strong quake struck near the Thai border in March 2011, killing more than 70.