A poignant memorial service in South Sudan for four Russian crew members killed when a U.N. peacekeeping helicopter was shot down on Friday.

Among those paying tribute at the U.N. Mission base near Juba International Airport: U.N. peacekeepers, Russian contractors and South Sudan's Deputy Defense Minister Majak D'Agoot.

Also in attendance was U.N. special representative, Hilde Johnson, who laid a wreath in tribute.

Johnson welcomed promises by South Sudan's government to investigate the crash.

(SOUNDBITE) (English) HILDE JOHNSON, SPECIAL REPRESENTATIVE OF THE UNITED NATIONS' SECRETARY GENERAL, SAYING:

" Both the vice president and the president of the Republic of South Sudan have personally conveyed this strong message to me on Saturday and they are committed to let nothing like this ever happen again."

The Russian-owned helicopter was apparently shot down by the South Sudanese army after being mistaken for a plane supplying rebel fighters in the area.

The bodies of the four crew members were flown home to Russia following the service.