BANGKOK -- Tens of thousands of migrant workers left Thailand for neigbouring countries after new restrictions were announced at the weekend and the country prepared to close many land border crossings late on Monday to curb the coronavirus outbreak.

At the same time, Thai workers from the countryside were also fleeing Bangkok after department stores, malls, dine-in restaurants, salons and other public places were ordered closed over the weekend.

Thai authorities have urged workers not to rush out of the cities in large numbers and to stay put in order to curb the spread of the disease.

“The mass traveling will increase the spread of the virus,” said Tawee Chotpitayasunondh, a senior advisor to the Thai Health Ministry.

Many land border crossings between Thailand and neighbouring countries will be open until late on Monday, allowing migrant workers to leave the country, a Thai interior ministry official said.

“Because many migrant workers are wanting to leave we will allow them to do so for just one day,” an interior official who does not wish to be named told Reuters.

“Tomorrow all crossings will be closed,” he said.

Thailand is estimated to have four to five million migrant workers, mainly from Laos, Myanmar and Cambodia.

Laos and Myanmar have yet to report cases of coronavirus.

Thai authorities started to shut some border crossings last week, aiming to close all 91 crossing points with Laos, Myanmar, Cambodia and Malaysia on Monday, allowing only trucks carrying goods to go through.

Stern measures, including a 22-day closure of department stores and many businesses in Bangkok and major Thai cities which started on Sunday, have led hundreds of migrant workers to head for the border.

“They cannot survive here without income so many decided to leave immediately,” said Suthasinee Kaewleklai, coorindator of the Migrant Workers Rights Network.

Some 7,000 workers from Myanmar left Thailand on Sunday alone, joining thousands who have left since last Wednesday, said Ye Min from the Aid Alliance committee, a non-profit that helps migrant workers in Thailand.

“People worried that they will get stuck. So, they came back to their own country,” he said.

Authorities in Myanmar, Laos and Cambodia have told returning workers to self-isolate for 14 days.

Thailand now has 721 coronavirus cases after recording 122 new cases on Monday. One has died since the start of the outbreak.