FIFA insisted conditions for migrant workers are changing in Qatar after World Cup sponsor Visa expressed its "grave concern".

One of FIFA's biggest partners spoke out on Wednesday and urged action to help migrant workers in the country.

The conditions for migrant workers involved in construction work for the 2022 World Cup in Qatar has come under increasing scrutiny but FIFA believes awarding the country the tournament has been a catalyst for "significant change".

A statement read: "FIFA has repeatedly urged publicly and with the highest authorities in Qatar that fair working conditions for all workers in Qatar are imperative.

"Migrant workers have been working for many global companies in Qatar for decades, yet only now is real change happening in their working conditions.

"While there are huge construction programs underway in Qatar that have no connection to the FIFA World Cup, it is clear that the FIFA World Cup is serving as a catalyst for significant change.

"FIFA, alongside trade unions and human rights organizations, will continue to urge the Qatari authorities to accomplish reforms and abolish the Kafala system. Ultimately, however, sustainable change in the whole country can only be reached in a collective effort with all stakeholders involved, including international companies and governments."

The comments from one of FIFA's biggest partners will increases the pressure on the world governing body, though, after Visa spoke out.

A statement read: "We continue to be troubled by the reports coming out of Qatar related to the World Cup and migrant worker conditions.

"We have expressed our grave concern to FIFA and urge them to take all necessary actions to work with the appropriate authorities and organisations to remedy this situation and ensure the health and safety of all involved."

Visa has been a FIFA partner since 2007 and last year signed a new deal until 2022, which includes the Qatar tournament.

The International Trade Union Confederation had also urged FIFA to improve conditions for migrant workers in Qatar.

ITUC general secretary Sharan Burrow said: "If FIFA is serious about this, they can turn it around. They can turn it around, but they choose not to."

FIFA has already said it was seeking "clarity from the Qatari authorities" after a BBC news team was arrested in Qatar while reporting on the plight of the migrant workers.

The BBC's Middle East business correspondent Mark Lobel was arrested in Doha, having been invited into Qatar by the prime minister's office.

Lobel said he and his crew were detained for a lengthy period and subject to "hostile" questioning after being the subject of two days of surveillance prior to their arrests.

In response, the Qatar government said the detentions were made for trespass and breaking Qatari laws.

"By trespassing on private property and running afoul of Qatari laws, the BBC reporter made himself the story," the Qatar government said.

"We sincerely hope that this was not his intention. Moreover, we deeply regret that he was unable to report the real story, which is that the government and the private sector are making significant progress in efforts to improve the lives and the labour conditions of guest workers in Qatar."

A FIFA spokesman said: "Any instance relating to an apparent restriction of press freedom is of concern to FIFA and will be looked into with the seriousness it deserves."