Seeking to stem an outbreak of the COVID-19 pandemic, more than half of Iraq's 18 provinces have declared curfews of several days.

Baghdad, the Arab world's second most populous capital with 10 million in habitants, imposed a curfew from Tuesday evening for six days.

But the government's social distancing efforts are facing a hurdle, as pilgrims defy restrictions to commemorate the anniversary of the death of revered Shiite Imam Musa al-Kadhim.

The anniversary, which will be marked on Saturday, typically draws millions of pilgrims from around the world each year to Baghdad, to visit and kiss the gold-domed shrine housing the imam's resting place on the banks of the Tigris River.

Traditionally, pilgrims converge on foot on the imposing complex to pray and take part in mourning ceremonies that lasts several days.

Top cleric Grand Ayatollah Ali Sistani has urged Iraqis not to gather in large numbers for prayers, where risk of contamination could be high, and declared the fight against the novel coronavirus a "sacred duty".

Iraq has imposed travel restrictions and shuttered shrines across the country, including that of Imam Kadhim.

On Wednesday, Iraqi troops stationed around the site tried to persuade fervent pilgrims to return home.

"It's for your own health that we're doing this," one soldier told an elderly woman in the street.

"No one can prevent us from visiting our imams! Not terrorism, not war, not a virus!" she shot back.

Musa al-Kadhim, the seventh of 12 imams venerated by Shiite Muslims, died in 799 while in detention by Abbasid caliph Harun al-Rashid.

At another checkpoint, a group of around 20 men waved flags bearing yellow and green religious emblems as they tried to make their way past soldiers blocking the street.

In contrast, the holy Shiite shrine city of Najaf, south of Baghdad, was markedly quiet.

The mausoleum of the Prophet Mohammad's son-in-law Ali was shut and its usually busy esplanade empty, an AFP photographer said.

Health authorities have reported 13 deaths and 164 infections in Iraq from the novel coronavirus.

However, many suspect the number of cases could be higher, as fewer than 2,000 people have been tested in a country of 40 million.

Iraqis have expressed fear over the impact of a large outbreak in the country, as years of conflict and poor investment have ravaged the country's health system.