Cairo international airport officials issued a security alert on Tuesday after receiving an anonymous threat to blow up a United Nations aircraft if the airport did not pay $20 million.

Airport security officials said an airport employee received an anonymous call early on Tuesday ordering him to prepare the money or a private UN plane on the runway near terminal four would be blown up.

The UN plane is generally used to transport officials between Cairo and other nations involved in refugee programmes and the global hunger campaign.

Officials said a security alert was immediately issued and a team of explosives specialists sent to inspect all private planes. They added that security measures had now been completed and no bomb had been found.