Ghanaian Vice-President John Dramani Mahama has been sworn in as the West African nation's leader following the sudden death of President John Atta Mills, in line with the country's constitution.
Mahama took the oath of office as head of state before a sombre parliament on Wednesday, hours after the announcement of Mills' death on Tuesday afternoon.
The swift adherence to Ghana's constitution on succession underlines the country's reputation as one of the most mature democracies in the region, commentators said.
"This is the saddest day in our nation's history. Tears have engulfed our nation and we are deeply saddened and distraught," Mahama said after being sworn in.
"I never imagined that one day that it would place our nation in such a difficult circumstance. I'm personally devastated, I've lost a father, I've lost a friend, I've lost a mentor and a senior comrade," he said.
"Ghana is united in grief at this time for our departed president."
The president's office said that Mills, who had celebrated his 68th birthday last Saturday, 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 Tuesday afternoon when his condition worsened.
Mills had returned from medical checks in the United States a few weeks ago.
He had won international praise as leader of a stable model democracy in Africa. Ghana remains the only Sub-Saharan country that Barack Obama, the US president, has visited as part of recognition for its democratic credentials.
The unexpected death of the president came months before he was due to stand for re-election in December.
|Mills had returned from medical checks in the US
a few weeks ago [AFP]
Ghana's election commission said Mills' death would not affect December's presidential and parliamentary elections.
"The election calendar remains unchanged - it's purely a party matter," Kwadwo Afari-Gyan, the elections chief, told Reuters.
He said it was up to the ruling National Democratic Congress (NDC) to find a candidate to replace Mills.
Trained as a lawyer and taxation expert, Mills had overseen Ghana's emergence as one of Africa's newest oil producers two years ago, winning plaudits both at home and abroad for his sound economic policies and commitment to democracy and good governance.
In March, Obama received Mills in the Oval Office and praised him and his country as "a good-news story" in Africa.
Nii Akuetteh, an Africa commentator based in Washington, DC, told Al Jazeera Mills had been credited with Ghana's "serious economic growth".
He said Mills "signed strong economic agreements with China" and that his "influence goes back because he served as vice-president" during former leader Jerry John Rawlings administration.
Ghana, the world's second-largest producer of cocoa and a major gold producer, started pumping oil in 2010 and posted double-digit growth in 2011.
Mills, who won a close-fought, two-round election in 2008 by beating off rival Nana Akufo-Addo of the then-ruling New Patriotic Party (NPP), was preparing to bid for a second term in December's polls, once again against arch-foe Akufo-Addo.