Security guards in Qatar are being subjected to "forced labour" conditions, working months sometimes years without a day off, Amnesty International said in a report released Thursday which called for an investigation before the Gulf state hosts the World Cup.

Thousands of migrant labourers from Africa and Asia work as poorly paid guards at offices, factories and construction sites in the Gulf state. Thousands more are expected to be taken on before the first World Cup in the Arab region starts on November 21. 

Amnesty said 34 current or former guards "described routinely working 12 hours a day, seven days a week -- often for months or even years on end without a day off".

One Bangladeshi guard told the group he did not get a day off for three years.    

Those who took a legal weekly day off often had wages cut, it added. Guards also lost money for taking a toilet break without getting cover, taking a day off sick or just wearing their uniform "improperly".

The men complained that they had to work outside in Qatar's notorious summer, when temperatures hit 50 degrees Celsius (122 Fahrenheit).

Many of the guards are from Uganda and Kenya and they told Amnesty that they were given more jobs in the heat and also received lower wages than others, particularly Arabic-speaking workers.  

Following previous criticism, Qatar in 2017 introduced a minimum wage, cut the hours that can be worked in heat and ended parts of a system which forced migrant workers to seek employers' permission to change jobs or even leave the country.

But Amnesty said there is still a "massive power imbalance" between employers and migrant workers with the security sector getting little attention. Unions are banned in Qatar.

"Physically and emotionally exhausted, workers kept reporting for duty under threat of financial penalties -- or worse, contract termination or deportation," said Stephen Cockburn, a social justice specialist for Amnesty.

At least three of the eight companies who employed the workers interviewed by Amnesty provided security for FIFA tournaments, including last year's Club World Cup and FIFA Arab Cup, the report said.

The Qatar organising committee said in a statement that three companies were found to be in "completely unacceptable" violation of labour rules and were hit with punishments including being put on a "blacklist to avoid them working on future projects."

They were also reported to the labour ministry. The committee said its safeguards were "unique even by international standards" but "will always have contractors attempting to beat the system, regardless of stringent regulations or monitoring."

The Labour Ministry said in a statement that it does take regular action against "unscrupulous" employers.

"These cases do not represent an underlying fault with the robust labour system now in place. The prevalence of rulebreaking companies has and will continue to decline as enforcement measures take hold and compliance increases among employers," it said.