Salvadoran president declares himself 'dictator' in apparent joke

El Salvador's President Nayib Bukele has on Twitter proclaimed himself "dictator" of the Central American country, in an apparent joke that has done little to dispel concerns about his increasing concentration of power.

The 40-year-old Bukele, a seasoned and often provocative user of social media, late on Sunday changed his Twitter profile to read "Dictator of El Salvador", in what appears to be a bid to mock critics who accuse him of having autocratic tendencies.

The office of Bukele, a vigorous proponent of Bitcoin who opinion polls show is one of the most popular leaders in the Americas, did not reply to a request for comment.

Erika Guevara-Rosas, Americas director of human rights group Amnesty International and a critic of Bukele, said his use of "mocking language" showed the president's contempt for those who "question or criticize him constructively", and urged him to build bridges rather than courting controversy on Twitter.

Bukele's administration came under fire from the United States this month after Salvadoran Supreme Court judges recently appointed by his party ruled that the president could seek a second consecutive term, which Washington saw as unconstitutional.

Last year, Bukele, who has nearly 3 million followers on Twitter, caused a furor by sending troops into the National Assembly to help push through law and order legislation in the impoverished country of around 6.5 million people.