Three days of mourning have been declared in Nigeria for 10 of the most senior army commanders who died when their military plane crashed.
Those killed near the south-eastern town of Obudu include eight major generals and two brigadier generals, the authorities said.
President Olusegun Obasanjo called the crash a "monumental tragedy" and is flying home early from Singapore.
Two other officers also died, while at least four survived, the military says.
There were 18 people on board the Dornier 228 aircraft when it crashed into a hill 18 nautical miles from Obudu after flying from the capital, Abuja.
The private meeting had been ordered by the new chief of army staff to discuss the challenges facing the military.
The BBC's Alex Last in Nigeria says it is thought the restructuring of the task force in the volatile, oil-rich Niger Delta would be one of the key issues for discussion; the other being the army's role in maintaining stability in the run-up to next year's elections.
A spokesman at the Nigerian defence headquarters, Brigadier General Felix Chukwuma, told the BBC the crash would affect the whole defence establishment:
"They are the top echelon in the army headquarters... It is a big loss, irreparable, but the army shall still wade on."
Captain Emeka Ozomena told the BBC it was too early to speculate on the causes of the crash. President Obasanjo has ordered an investigation.
More than 200 people died in two air disasters last year, leading many to question the safety of Nigerian planes.
After the disasters, several airlines were grounded while safety checks were carried out.