The US and the European Union voiced concern over Nigeria's decision to indefinitely ban Twitter after the US social media giant deleted a tweet from the president's account for violating its rules.
International human rights groups have also condemned the move, which followed previous attempts by the government of Africa's most populous country to regulate social media.
Nigerian telecoms operators complied with a government directive Friday to suspend access to Twitter indefinitely.
The diplomatic missions of the EU, US, Britain, Canada, and Ireland issued a joint statement late Saturday condemning the ban.
"Banning systems of expression is not the answer," it said.
"Precisely the moment when Nigeria needs to foster inclusive dialogue and expression of opinions, as well as share vital information in this time of the COVID-19 pandemic."
"The path to a more secure Nigeria lies in more, not less, communication," it added.
More than 39 million Nigerians have a Twitter account, according to NOI polls, a public opinion and research organisation based in Nigeria.
The platform has played an important role in public discourse in the country, with hashtags #BringBackOurGirls after Boko Haram kidnapped 276 schoolgirls in 2014, and #EndSARS during anti-police brutality protests last year.
The government's suspension came after Twitter on Wednesday deleted a remark on President Muhammadu Buhari's account in which he referred to the country's civil war four decades ago in a warning about recent unrest.
The 78-year-old president, a former general, referred to "those misbehaving" in recent violence in the southeast, where officials blame a proscribed separatist group IPOB for attacks on police and election offices.
"Those of us in the fields for 30 months, who went through the war, will treat them in the language they understand," the president had posted on Twitter.
The presidency denied late on Saturday that the Twitter suspension was a response to the removal of that post.
"There has been a litany of problems with the social media platform in Nigeria, where misinformation and fake news spread through it have had real world violent consequences," a presidency spokesman Garba Shehu said in a statement.
Shehu said the removal of Buhari's tweet was "disappointing" and said "major tech companies must be alive to their responsibilities."
Twitter said it was "deeply concerned by the blocking of Twitter in Nigeria."
"Access to the free and #OpenInternet is an essential human right in modern society. We will work to restore access for all those in Nigeria who rely on Twitter to communicate and connect with the world. #KeepitOn," the company said in a statement.
"VPN app" was the second most searched trend Saturday on Google in Nigeria, as virtual private networks can enable Twitter users to bypass the ban.
Nigeria warned however that it would prosecute violators.
"Attorney General of the Federation and Minister of Justice, Abubakar Malami, has directed for immediate prosecution of offenders of the Federal Government ban on Twitter operations in Nigeria," spokesman Umar Jibrilu Gwandu said.
Amnesty International condemned the ban, calling on Nigeria to "immediately reverse the unlawful suspension".
"This repressive action is a clear attempt to censor dissent & stifle the civic space," Human Rights Watch researcher Anietie Ewang said.
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