People arrive at the site of a car accident in downtown Cairo. AFP

At least 20 people have been killed when a speeding car driving against traffic crashed into three others causing a huge explosion in Cairo, the Egyptian health ministry said on Monday.

The car collision happened just before midnight on Sunday outside the National Cancer Institute in central Cairo also wounding 47 people, the ministry added.

Four of those killed in the deadly crash remain unidentified.

Between "three and four (of the injured) are in critical condition in the intensive care unit," Khaled Megahed, a spokesman for the health ministry, told an early Monday news conference.

He said they suffered from "several burns of varying degrees."

Body parts were also retrieved from the scene, he added.

Social media users posted footage of cars ablaze at the scene and of patients being evacuated from the Cancer Institute, which was severely damaged and charred in the explosion.

Megahed said that 78 cancer patients from the institute were moved to other hospitals to continue their treatments.

Egypt's prosecutor general has ordered an investigation to determine the causes of the crash.

Deadly road accidents owing to driver error and dilapidated infrastructure are common in Egypt with over 3000 killed in more than 8400 crashes in 2018, according to official figures published earlier this year.