Ghana's new president, Nana Akufo-Addo, has apologised for imitating passages from speeches by Bill Clinton and George W Bush during his inaugural address.

Opposition leader Akufo-Addo, a 72-year-old former human rights lawyer, won the tightly-contested presidential election after defeating President John Mahama last month by securing 53.8% of the vote against Mahama's 44.4%, becoming president-elect in his third attempt.

Taking oath of office at a ceremony attended by dozens of African leaders in the capital Accra on 7 January, it soon became apparent that passages from the new leader's speech had been lifted from two ex-US presidents, Clinton and Bush's own speeches of 1993 and 2001 respectively.

On Sunday (8 January), the president's office issued an apology, stating the plagiarism was a "complete oversight, and never deliberate".

"I unreservedly apologise for the non-acknowledgement of this quote to the original author. It was a complete oversight, and never deliberate," presidency's communication director Eugene Arhin said, according to DPA news agency.

What speeches did Nana Akufo-Addo 'plagiarise'?

Social media users have pointing out similarities between Akufo-Addo's speech and that of the two American leaders.

First, the Ghanaian said: "Though our challenges are fearsome, so are our strengths. Ghanaians have been a restless, questing, hopeful people. And we must bring to our task today the vision and will of those who came before us."

Here's what Clinton told the nation in his 20 January 1993 inauguration speech: "Though our challenges are fearsome, so are our strengths. And Americans have ever been a restless, questing, hopeful people. We must bring to our task today the vision and will of those who come before us."

Later, Akufo-Addo declared: "I ask you to be citizens: citizens, not spectators; citizens, not subjects; responsible citizens building your communities and our nation."

This seemed to the inaugural speech Bush delivered in on 20 January 2001. "I ask you to be citizens: citizens, not spectators; citizens, not subjects; responsible citizens building communities of service and a nation of character," he told fellow Americans at the time.