AFP / Getty Images, file
Ghanaian President John Atta Mills is shown last August.
ACCRA -- Ghana's President John Atta Mills has died unexpectedly, a presidential statement said, and an aide said his death occurred on Tuesday after he took ill on Monday night.
The death of the president of the world's No. 2 cocoa grower comes months before Mills was due to stand for re-election at the helm of the West African country that posted double-digit growth in 2011 and has been praised for its strong democracy in a turbulent region.
Vice President John Dramani Mahama was scheduled to be sworn in later Tuesday. According to the country's constitution, Mahama will complete Mills' term that was due to end with elections in December.
"It is with a heavy heart ... that we announce the sudden and untimely death of the president of the Republic of Ghana," a statement sent to Reuters by the president's office said.
It said that Mills, 68, died a few hours after being taken ill but no further details were given.
A presidential aide, who asked not to be named, said the president had complained of pains on Monday evening and died early on Tuesday afternoon when his condition worsened.
Mills, who oversaw the start of oil production in Ghana, returned from medical checks in the United States several weeks ago.
The BBC reported he had recently suffered from throat cancer.
Mills was married to Ernestina Naadu Mills, an educator, and has a son, Sam Kofi Atta Mills, according to his official online profile.
In March, President Barack Obama received the Ghanaian president in the Oval Office and praised him and his country as "a good-news story" in Africa.
On Tuesday, the U.S. State Department said it "learned with sadness" about Mills' death.
"Our thoughts go to his family and to the people of Ghana, who have lost a beloved leader," said Victoria Nuland, State Department spokeswoman.
Ghana's election commission said December's presidential and parliamentary elections would go ahead as planned.
"The election calendar remains unchanged - it's purely a party matter," election chief Kwadwo Afari-Gyan told Reuters, explaining that it was up to the ruling National Democratic Congress to find a candidate to replace Mills.
Ghana has seen democratic elections decide its leadership no fewer than four times since the last military coup in 1981, a rare feat in a region where power is still just as often determined by the bullet as by the ballot.
Neighbor Ivory Coast has not been so peaceful, suffering months of violence last year after a disputed election. Near-neighbors Liberia and Sierra Leone suffered years of war.
A glance at Ghana's recent history:
July 1960: Kwame Nkrumah becomes president of the Republic of Ghana, months after a republican constitution is ratified by a referendum. Nkrumah is overthrown after a military coup in February 1966.
August 1969: A new constitution is ratified leading to a transfer of power to the civilian government of Kofi Busia. Busia is ousted in coup in January 1972 led by Colonel Ignatius Acheampong. General Frederick Akuffo takes over in 1978.
June 1979: Akuffo is deposed in a coup led by Flight Lieutenant Jerry Rawlings. Elections are held and in September Rawlings hands over power to a new president, Hilla Limann. Limann is also overthrown in coup in 1981, again led by Rawlings, after two years of weak economic policies. Rawlings is elected president in November 1992.
June 1994: Leaders of Ghana's warring northern tribes sign a peace accord after fighting erupted in the north in February, pitting landless Konkombas against three allied tribes. Independent sources estimated up to 5,000 people were killed by mid-April.
January 2001: Former opposition leader John Kufuor is sworn in as president after Rawlings served the two elected terms he was allowed.
June 2007: London-based Tullow Oil Plc says it has found up to 600 million barrels of oil offshore.
January 2009: Electoral Commission declares John Atta Mills winner after he defeated Nana Akufo-Addo of the ruling New Patriotic Party in run off presidential elections.
July 2009: Visiting U.S. President Barack Obama assures Africa it will not be sidelined from world affairs and hails democratic Ghana as a model for other African countries.
December 2010:Mills opens the valves in a ceremony at a floating oil platform off the country's Atlantic coast. Initial production of around 120,000 bpd will rank Ghana as sub-Saharan Africa's seventh largest producer.
July 2011: Mills is chosen as ruling National Democratic Congress party's candidate for the 2012 presidential election, defeating Nana Konadu Agyemang-Rawlings, wife of the former president.
December 2011: Ghana says it has exported 23.5 million barrels of crude oil from the Jubilee oilfield in its first year of production. Tullow Oil is the lead company of the consortium operating the Jubilee field.
July 24, 2012: Mills dies in office.
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