At least 130 million people in Bangladesh were left without power on Tuesday after a grid failure caused widespread blackouts, the government's power utility company said.

Bangladesh has suffered a major power crisis in recent months as a result of higher global energy prices following Russia's assault on Ukraine, and has imposed regular cuts to conserve electricity.

But it remained unclear what caused Tuesday's unscheduled blackout, which hit more than 80 percent of the country shortly after 2pm local time, according to the Power Development Board.

Apart from some locations in Bangladesh's northwest, "the rest of the country is without power", said spokesman Shamim Ahsan.

The normally brightly lit streets of central Dhaka and other cities were dark on Tuesday evening.

Ahsan said 130 million people or more were without electricity and it remained unclear what had caused the fault.

"It is still under investigation," he said, adding that a technical malfunction was the probable cause.

Another official said later that only 60 percent of the poor country, which is home to factories supplying garments for Western brands, had been affected.

Since then half of those affected had had their power restored by the evening, said ABM Badruddoza, spokesman of the state-run power grid company.

Junior technology minister Zunaid Palak said on Facebook that power would be restored by 8pm in the capital Dhaka, a megacity home to more than 22 million people.

Prices of energy as well as food and other staples have soared worldwide in the wake of Russia's attack on Ukraine in February, including in Asia.

This has wrought havoc on Bangladesh's electricity grid in recent months, with utilities struggling to source enough diesel and gas to meet demand.

A depreciating currency and dwindling foreign exchange reserves left Bangladesh unable to import sufficient fossil fuels, forcing it to close diesel plants and leave some gas-fired power stations idle.

The government imposed lengthy power cuts to conserve existing stocks in July, with outages lasting up to 13 hours a day at their peak. (AFP)