Twitter is "coming of age" in Africa, according to a report by communications firm Portland, with the platform being most widely used for political debate.

The report by the London-based communication agency - the third annual "How Africa Tweets" - found almost one in 10 of the most popular African hashtags in 2015 related to political issues and politicians.

This figure outstrips political discussion and debate on the social media platform in the United States (US) and United Kingdom (UK), where only 2% of hashtags were political. The top political hashtag in Africa of 2015 was focused on the highest profile election on the continent last year - #NigeriaDecides.

Political discussions have become the second most popular form of discussion in Africa, with Nigeria, South Africa, Ethiopia, Burundi and Egypt the most active in these political conversations.

Interest in politics also transcends national borders, with hashtags about the Nigerian elections and strife in Burundi among some of the most popular hashtags across Africa.

Portland analysed 1.6 billion geo-located tweets and the top 5,000 hashtags on the continent in order to obtain a full picture of Africa's Twitter usage. It found tweets about showbiz and entertainment were the most popular on the continent, representing 20% of all hashtags.

English is by far the most dominant language on Twitter in Africa, with 77% of the top 5,000 hashtags in English. Other top languages, Arabic and French, were tweeted significantly less, at 7% and 4% respectively.

Another key finding was that Twitter in Africa is used distinctly less for commercial campaigns than in other parts of the world, with commercial hashtags like brand names and promotional offers 25 times less prominent in Africa than, for example, in the US.

In terms of the most active country on Twitter, Egypt came in first, with its 28% of all geolocated Twitter volume amounting to about 450 million tweets. Nigeria had 350 million geolocated tweets, South Africa 325 million, Kenya 76 million and Ghana 65 million. In total, the 1.6 billion geolocated tweets in Africa in 2015 was a 34-fold increase from Portland's initial research in 2012.

"Our previous studies showed that Twitter in Africa was much more of a space for social interaction or frivolous banter. This study, our third, demonstrates that the platform is coming of age with the prevalence of serious debate about politics and government," said Mark Flanagan, Portland's senior partner for content and digital strategy.

"Excitingly, our report also hints at the coming together of Africans across boundaries to comment on and discuss common issues. How to successfully engage with these emerging pan-African online communities represents a challenge for all brands and organisations seeking to build their presence in this space," said Allan Kamau, head of Portland's Nairobi office.