Imprisoned Iranian human rights lawyer Nasrin Sotoudeh has been hospitalised after being "severely weakened" after an over 40-day hunger strike, her husband said on Saturday.

She was transferred to the cardiac care unit shortly after being taken to the emergency ward of Tehran's Taleghani hospital, Reza Khandan told AFP over telephone.

"We were allowed to see her for a few moments," he added. "She was severely weakened, lost a lot of weight and had sunken eyes".

Sotoudeh has been on a hunger strike for more than 40 days, according to Khandan.

The strike is aimed at calling for the freeing of political prisoners and directing attention towards their condition during the Covid-19 pandemic, said an August 11 statement by Sotoudeh published by her husband on social media.

The virus has so far killed over 24,000 and infected close to 420,000 Iranians, according to official figures.

Khandan told AFP he worried for his wife as the hospital "is not a safe place vis-a-vis the coronavirus" and lacks "proper isolation" with many infected patients.

Sotoudeh has been on hunger strike for more than 40 days
Sotoudeh has been on hunger strike for more than 40 days AFP / BEHROUZ MEHRI

But her last scan has not shown a sign of infection, he added.

Sotoudeh, 57, is a co-laureate of the European Parliament's prestigious Sakharov Prize.

She is serving a 12-year sentence in Tehran's Evin Prison after she defended women arrested for protesting compulsory hijab laws.

"It is all very difficult," Khandan said, having just returned home from the hospital around midnight.

"The prison does not cooperate, they don't properly answer when you ask about (prisoners') condition. They had not even told us" of her hospitalisation, he added.

Sotoudeh's family were notified of her condition through one of her fellow inmates.

Sotoudeh won the Sakharov Prize in 2012 for her work on high-profile cases including those of convicts on death row for offences committed as minors.

She spent three years in prison after representing dissidents arrested during mass protests in 2009 against the disputed re-election of the ultra-conservative president Mahmoud Ahmadinejad.