A powerful earthquake that struck Myanmar on Sunday left at least two dead and five missing, a government official said, after the tremor sparked panic in the central city of Mandalay.

"According to the information we have so far, two people died and three were injured because of the earthquake, while five are still missing," the official in the capital Naypyidaw told AFP, asking not to be named.

He said the missing were workers flung into the Irrawaddy river when the quake shook the bridge they were building in an area north of Mandalay, the country's second-largest city.

One man died and three were injured by buildings collapsing in a small town in central Sagaing region. A woman was also killed by falling debris from a brick wall in a village north of Mandalay.

The shallow 6.8-magnitude quake hit around 116 kilometres (72 miles) north of Mandalay at a depth of just 10 kilometres, the US Geological Survey (USGS) said. It initially put the magnitude of the quake at 7.0.

It was followed by a series of strong aftershocks.

"I ran from my bed carrying my daughter out to the street. There were many people in the road. Some were shouting and others felt dizzy," Mandalay resident San Yu Kyaw told AFP by telephone.

"People are now scared of more earthquakes. Especially those who live or run businesses in high-rise buildings are desperate and don't know what to do," he said.

Construction standards are generally poor in the country formerly known as Burma, one of Asia's most impoverished nations.

A large crack stretching from the second to the sixth floor of Mandalay's highest building, the 25-storey Mann Myanmar Plaza, appeared after the quake, a local resident told AFP.

He said people were afraid to enter the structure and it remains closed.

The USGS issued a yellow alert, saying "some casualties and damage are possible" but that the impact should be relatively localised.

The quake hit at 7:42 am (0112 GMT) and was followed by two shallow 5.0-magnitude aftershocks within 20 minutes, according to the USGS.

"The quake was quite strong. I was shopping in the market at the time and I saw women crying in fear when they felt it. We expect more quakes are coming. Everybody is afraid," said 23-year-old Win Win Nwe, a resident in the small town of Shwebo, north of Mandalay.

She said there were fears that several people had been injured in a nearby town.

It comes little more than a week before US President Barack Obama is due in Myanmar on a historic visit, as the West begins to roll back sanctions to reward a series of dramatic political reforms under President Thein Sein.

The quake was felt in neighbouring Thailand, including in the capital Bangkok, according to reports on social media websites.

It struck around 572 kilometres east of the Bangladeshi capital of Dhaka, one of the world's biggest cities.

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, resulting in landslides, liquefaction and the loss of 610 lives.

Kyaw Kyaw Lwin, an official at the National Earthquake Information Division in the capital Naypyidaw, said it was the strongest quake in the area since a 6.0-magnitude quake in 1991.

More than 70 people were killed in March 2011 when a powerful 6.8-magnitude quake struck Myanmar near the borders with Thailand and Laos, reducing homes and government buildings to rubble and affecting thousands of people.

Aid workers at the time praised Myanmar's regime for its speedy response to that quake, in contrast to the aftermath of previous disasters to strike the country under the old military junta, which ruled the country for decades.