Media playback is unsupported on your device Media caption There are an estimated 400,000 Cambodian workers in Thailand

Tens of thousands of Cambodians are fleeing neighbouring Thailand amid fears the new military leadership will crackdown on migrant workers.

The International Organization for Migration (IOM) tweeted that 70,000 people crossed the border this week.

A spokesman for the agency said many migrants were fearful about what would happen to them if they stayed.

Several migrants have reportedly been fired from jobs and sent home since the army took power in a coup last month.

But the authorities have denied rumours swirling of people being beaten up or even shot dead.

'Revamp' system

Many Cambodians have been massing in border areas, reportedly transported in some cases in buses laid on by the Thai authorities.

The IOM said hundreds of trucks, buses and trains were being used to take the workers back to their home towns.

"The overwhelming priority is to secure enough large vehicles to prevent people being stuck here for a long time in less than ideal conditions," said the IOM's Brett Dickson in the border town of Poi Pet.

"Many of these people are severely economically disadvantaged and have spent all their savings, if they had any, to get this far."

There are believed to be at least 150,000 Cambodian migrants working in Thailand, though only 80,000 are there legally.

Thai Foreign Ministry spokesman Sek Wannamethee said the authorities "realise the importance of migrant workers... toward driving Thailand's economy forward".

"As a result, we would like to revamp and integrate the management system, as well as get rid of exploitation from smugglers, in a bid to prevent abuses of the workers and human trafficking problems".

But a Cambodian human rights body accused the Thai military of violating the workers rights, by "forcefully" expelling them and "placing them in crowded trucks".