Investigators work on spot next to a shattered shop window in downtown Cairo, Egypt, Feb. 3, 2015. A blast occurred at Talaat Harb square in downtown Cairo, leaving no casualties, an official source at Cairo Security Directorate was quoted by MENA as saying. (Xinhua/Cui Xinyu)

CAIRO, Feb. 3 (Xinhua) -- An explosion was heard in the central downtown of Egyptian capital Cairo on Tuesday, official news agency MENA reported.

The blast occurred at Talaat Harb square in downtown Cairo, leaving no casualties, an official source at Cairo Security Directorate was quoted by MENA as saying.

Earlier sources said primitive explosive device was behind the blast.

Meanwhile, Khalid Youssef, assistant interior minister at Cairo Security Directorate, told MENA that the bomb was planted at a corridor leading to an electricity room at Harb Street.

Eyewitnesses told state-run Nile TV that the blast destroyed the wall in front of two stores.

A wave of bombing attacks hit Egypt after the ouster of the Islamist president Mohamed Morsi in July 2013 by the army.

The militants killed hundreds of police and soldiers in retaliation of harsh crackdown on Morsi's supporters which left nearly 1,000 killed and thousands in prison.

Elsewhere in Cairo, security measures were beefed up at Cairo International Airport after two bombs were reported to be found at terminals on Tuesday morning, according to independent Youm7 website.

The two bombs were made of primitive electronic devices, Youm7 quoted sources at the airport as saying.