South Korea reported a sharp jump in coronavirus cases on Sunday, while Italy and Iran took drastic containment steps as worldwide fears over the epidemic spiralled higher.

The contagion's spread prompted the World Health Organization (WHO) to warn that Africa's unprepared health systems left the continent vulnerable to the COVID-19 disease, which spilled out of China and has infected more than 77,000 people in more than 25 countries.

Already one of the worst-hit nations outside of China, South Korea reported 123 new cases Sunday, taking its fast-rising total to 556. Its death toll also rose to four with two additional fatalities.

The higher toll came a day after Prime Minister Chung Sye-kyun said the nation of around 51 million people faced a "grave" situation.

The Shincheonji Church of Jesus in the southern city of Daegu -- considered by many a cult -- has emerged as a hotbed of contagion, with hundreds of members infected.

Prime Minister Chung called on Koreans to refrain from attending large gatherings including religious services.

Other South Korean cases involved many under hospital treatment for mental health issues, an employee with electronics giant Samsung, and eight people who just returned from a trip to Israel.

Italy and Iran began introducing the sort of containment measures previously seen only in China, which has put tens of millions of people under quarantine lockdown in the epicentre province of Hubei.

More than 50,000 people in about a dozen northern Italian towns near the business hub of Milan were urged by authorities to stay home, shuttering shops and schools.

Among dozens of cases, Italy on Friday became the first European country to report one of its nationals had died from the virus -- a 78-year-old retired bricklayer in the region of Veneto.

That was followed Saturday by the death of a 77-year-old woman in Lombardy.

Italian Prime Minister Giuseppe Conte said the government was weighing "extraordinary measures" to halt further infections.

Officials said all patients in Lombardy were linked to a 38-year-old man in intensive care in the town of Codogno, whom Italian media say dined in January with a friend who had returned from China.

The friend has since tested negative, however, illustrating mounting frustration among authorities worldwide over exactly how the virus spreads and the duration of its incubation period.

China reported another 97 deaths in its daily update on Sunday, taking its total to 2,442, plus another 648 new infections. Nearly 80,000 infections have been reported worldwide.

China's infection rate has slowed sharply from earlier in the epidemic, but repeated Chinese flip-flopping over counting methods has sowed confusion over its data.

Iran ordered the closure of schools, universities and cultural centres across 14 provinces from Sunday following five deaths in the Islamic Republic -- the most outside East Asia and the first in the Middle East.

Iran's outbreak surfaced on Wednesday and has quickly worsened with 28 cases confirmed.

"The concern is... That we have seen ... A very rapid increase (in Iran) in a matter of a few days," said Sylvie Briand, director of the WHO's global infectious hazard preparedness department.

Iran's government also ordered all "art and cinema events" nationwide cancelled until the end of the coming week.

Iraq on Thursday clamped down on travel to and from Iran, and flag carrier Kuwait Airways has suspended flights to the country.

Although Egypt is the only African country with a confirmed case of COVID-19, the WHO warned that the continent's health systems were ill-equipped to cope with a potential major outbreak and urged more cooperation among the African Union.

WHO chief Tedros Adhanom Ghebreyesus said necessary treatment tools such as respiratory support machines are "in short supply in many African countries and that's a cause for concern".

The US State Department said global anxiety was being stoked by a coordinated effort by thousands of Russian-linked social media accounts to spread conspiracy theories that the outbreak was a US-orchestrate ploy to damage China, officials said.

Russia's foreign ministry dismissed the allegation as "deliberately false".