At least 49 foreign workers died when fire ripped through their accommodation block in the Kuwaiti city of Mangaf.

The nationalities of those who died were not immediately disclosed by authorities.

India's ambassador visited hospitals where workers were being treated for injuries sustained in the fire.

One hospital treated more than 30 Indian citizens, the Indian embassy wrote on social media, adding that at least 47 workers had already received treatment across a number of facilities.

Several Indians, including from the southern state of Kerala, were reported to have died in the fire, according to a letter written by Kerala Chief Minister Pinarayi Vijayan to India's foreign minister that was shared with the press.

A government agency for Keralites living outside the state said it had been told by the Indian community in Kuwait that 41 Indians, including 11 from Kerala, had lost their lives.

Kuwait's ruler Emir Sheikh Meshal al-Ahmad al-Sabah ordered an immediate investigation into the cause of the fire and pledged to hold accountable any officials found responsible.

Visiting the site, Kuwait's Deputy Prime Minister Sheikh Fahad Yusuf Saud Al-Sabah accused property owners of committing violations that contributed towards such incidents.

"The greed of real estate owners is what leads to these matters," he said.

It was not clear what specific violations he was referring to, or if any violations had taken place at the building in question.

Low-paid, blue-collar workers in the Gulf often live in overcrowded accommodation.

Local authorities did not say what kind of employment the victims were engaged in, though like in other Gulf states, Kuwait relies heavily upon foreign labour, including from South and South-East Asia, in industries like construction.

An Egyptian who survived the fire and worked as a driver in Kuwait told local media the fire had started on a lower floor and that those on higher levels were unable to escape after the building filled with thick smoke.

Three of 11 Filipino workers in the building were brought to hospitals, while the status of five remained unclear and three were safe, the Philippine Department of Migrant Workers said in a statement..

The interior ministry, which confirmed the death toll had risen to 49, was investigating the circumstances surrounding the incident, searching the site for victims and working to identify those who had died, state media reported.

The blaze was first reported to local authorities at 6am local time on Wednesday.

State television reported that many people had died from smoke inhalation, and dozens were rescued.

It said the building housed a large number of workers.

A senior Kuwaiti police commander said authorities had warned against housing too many workers in a single accommodation, but did not say whether regulations had been flouted.

Indian Prime Minister Narendra Modi described news of the fire as saddening.

"My thoughts are with all those who have lost their near and dear ones. I pray that the injured recover at the earliest," he wrote on social media.

Reuters