Iran's novel coronavirus death toll has surpassed 20,000, the government said Wednesday, six months after announcing the start of what quickly became the Middle East's deadliest outbreak.

The health ministry said COVID-19 claimed 153 more lives in the past 24 hours, bringing the country's overall toll to 20,125 dead.

Its spokeswoman, Sima Sadat Lari, told a televised news conference there had been another 2,444 cases of infection in the last 24 hours.

The Islamic republic has now reported 350,279 coronavirus infections since announcing its first cases -- two deaths in the Shiite holy city of Qom -- on February 19.

Lari described the situation as "concerning" in 26 of Iran's 31 provines, among them Tehran.

She also stressed health protocols should be observed during the holy Shiite mourning month of Moharram, which starts on Friday.

"In no case should Moharram ceremonies be held in closed spaces," she said.

There has been scepticism at home and abroad about Iran's official figures, amid concerns the real toll could be much higher. 

Authorities have not imposed a mandatory lockdown on the population across Iran.

Schools were shut, public events cancelled and travel between provinces banned in March.

Restrictions were gradually lifted in April as the coronavirus pandemic exacerbated a sharp downturn for Iran's sanctions-hit economy.

But deaths and infections have risen in the Islamic republic since hitting a months-long low in May, leading to a reimposition of some protocols.