Progress M-02M took off Thursday at 22:37 Moscow time (18:37GMT) on board a Soyuz-U carrier rocket and separated from the rocket nine minutes later.
"According to our data, the separation was successful. The Progress has been switched to an automatic flight regime," the official said.
He added that it would take the spacecraft five days instead of the usual two to reach the ISS because a series of flight tests was planned.
The freighter is equipped with an on-board digital control system, and is the second in a new series to replace the analog-controlled Progress spacecraft.
The ship will deliver 2.5 tons of cargo to the ISS, including a new Orlan-MK spacesuit, food, fresh fruit and vegetables, medical and scientific equipment.
Docking with the ISS is scheduled for May 12 at 23:23 Moscow time (19:23GMT), the spokesman said.