Television station Joy News broadcast cell phone footage from the crash scene showing smouldering wreckage in a heavily forested area earlier in the day, before it was revealed that ministers Edward Omane Boamah and Ibrahim Murtala Muhammed were among the dead.

Boamah became President John Mahama's defence minister shortly after Mahama's swearing-in in January.

Muhammed, 50, was serving as the minister of environment, science and technology.

Everyone onboard was killed in the accident, authorities said, while Ghanaian media reported that the helicopter was on its way to an event on illegal mining -- a major environmental issue in the west African country.

"The president and government extend our condolences and sympathies to the families of our comrades and the servicemen who died in service to the country," said Mahama's chief of staff Julius Debrah.

The Ghanaian Armed Forces said investigations had been launched to determine the cause of the crash of the Z9 helicopter in the Ashanti region.

Boamah was leading Ghana's defence ministry at a time when jihadist activity across its northern border in Burkina Faso has become increasingly volatile.

While Ghana has so far avoided a jihadist spillover from the Sahel -- unlike neighbours Togo and Benin -- observers have warned of increased arms trafficking and of militants from Burkina Faso crossing the porous border to use Ghana as a rear base.

A medical doctor by training, Boamah's career in government included stints as communications minister during Mahama's previous 2012-2017 tenure. Before that, he was the deputy minister for environment.

Mahama was "down, down emotionally", Haruna Iddrisu, Ghana's education minister, told reporters outside the presidency after news broke of the crash.

- Illegal mining -

The military had reported earlier Wednesday that an air force helicopter had dropped off the radar after taking off from Accra just after 9:00 am local time (0900 GMT). It had been headed towards the town of Obuasi, northwest of the capital.

The statement had said that three crew and five passengers were aboard, without specifying at the time that the ministers were among them.

Alhaji Muniru Mohammed, Ghana's deputy national security coordinator and former agriculture minister, was among the dead, along with Samuel Sarpong, vice chairman of Mahama's National Democratic Congress party.

Muhammed, the environment minister, was at the helm as the country battles a scourge of illegal, informal gold mining that has ravaged farmlands and contaminated water.

"Galamsey", as the practice is locally known, has been threatening cocoa production in particular and became a major issue in the election that saw Mahama elected last year.

The establishment earlier this year of the Ghana Gold Board and the banning of foreigners from the local gold trade were seen as the first concrete signs of a crackdown on the practice by the new administration.

As Ghana has pursued increased diplomacy with Burkina Faso, Mali and Niger -- all ruled by juntas who have broken with the ECOWAS west African regional bloc -- Boamah led a delegation to Ouagadougou in May.

He had been set to release a book titled "A Peaceful Man in an African Democracy", about former president John Atta Mills, who died in 2012.

All flags were to be flown at half-mast, Debrah said, while the presidency said Mahama had cancelled his official activities for the day.

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