The evening crash of an Antonov plane at the airport was due to "a technical fault during take-off," the office of the Sudanese army spokesman said in a statement, Xinhua reported.
The nine killed include four military personnel, but a girl survived the crash, according to the statement.
Sudan has been witnessing deadly clashes between the Sudanese army and the paramilitary Rapid Support Forces in the capital Khartoum and other areas since April 15.
The Port Sudan airport, located about 890 km east of Khartoum, has been used as the country's main airport after Khartoum International Airport became out of service because of armed clashes between the warring parties.