A Su-25 Frogfoot close-support aircraft exploded in the air on Thursday in the Primorye Territory about 143 kilometers (90 miles) from the port of Vladivostok. The pilot died in the crash.
"According to the preliminary investigation, the crash of a Su-25 combat aircraft over the Novoselskoye testing grounds was caused by the explosion of an S-8 rocket during its launch," the source said.
An investigation into the cause of the incident has been launched and a special investigation commission is to work at the crash site for at least nine days.
Investigators have found the plane's "black box" and are currently decoding it, the source said, adding that it may take a month to prepare the final report on the results of the investigation.
Russia's Air Force has suspended all Su-25 strike aircraft flights following the incident and until the investigation is complete, an Air Force spokesman said on Thursday.
The Su-25 is a single-seat, twin-engine jet aircraft developed by the Sukhoi Design Bureau to provide close air support for ground troops.
The aircraft is reported to have experienced a number of accidents in operational service caused by system failures attributed to the salvo firing of weapons.
Developed in the 1970s, the S-8 is an 80-mm (3.15 in) rocket used by fighter bombers and helicopters. The system entered service in 1984 and is produced in a variety of subtypes with different warheads.
The S-8 is generally carried in rocket pods, carrying either seven or 20 rockets.
Thursday's incident is the first Su-25 crash for two years. The most recent crash involving a Su-25 plane occurred in June 2006 in southwest Russia near the border with Ukraine. The pilot also died in the crash.
On May 21, 2005, a Su-25 crashed in Tajikistan. The pilot managed to eject from the plane and an investigation later established that the accident had been caused by technical problems.
The Su-25 aircraft has been in service with the Russian Air Force for more than 25 years. In 1999, Russia adopted a program to upgrade part of its aging Su-25 fleet. The Russian Air Force received the first six modernized planes, Su-25SM, in December 2006.
