Bangladesh's Prime Minister Sheikh Hasina has won a fifth term in power with her party taking three-quarters of seats in parliament, election officials said Monday after polls boycotted by the opposition as a "sham".

"The Awami League has won the election," said Moniruzzaman Talukder, a joint secretary of the Election Commission a day after a vote boycotted by the opposition, with initial reports suggesting a meager turnout of some 40 percent.

Talukder said Hasina's party had won 223 seats, but support of other lawmakers including from allied parties, means Hasina's actual control over the 300-seat parliament is even higher, analysts said.

"This is a one-party parliament," Ali Riaz of Illinois State University told AFP, adding that "only the allies of the Awami League had the opportunity to participate".

Hasina has presided over breakneck economic growth in a country once beset by grinding poverty, but her government has been accused of rampant human rights abuses and a ruthless opposition crackdown.

Her party faced almost no effective rivals in the seats it contested, but it avoided fielding candidates in a few constituencies, in an apparent effort to avoid the legislature being branded a one-party institution.

The opposition Bangladesh Nationalist Party, whose ranks have been decimated by mass arrests, called a general strike and, along with dozens of others, refused to participate in a "sham election".

Hasina, 76, who had called for citizens to show faith in the democratic process, branded the BNP "a terrorist organisation" after she voted on Sunday.

BNP head Tarique Rahman, speaking from Britain where he lives in exile, called the result "a disgrace to the democratic aspirations of Bangladesh", in a social media post, alleging he had seen "disturbing pictures and videos" backing his claims.

Meenakshi Ganguly, from Human Rights Watch, said Sunday that the government had failed to reassure opposition supporters that the polls would be fair, warning that "many fear a further crackdown".

Politics in the country of 170 million people was long dominated by the rivalry between Hasina, the daughter of the country's founding leader, and two-time premier Khaleda Zia, wife of a former military ruler.

Hasina has been the decisive victor since returning to power in a 2009 landslide, with two subsequent polls accompanied by widespread irregularities and accusations of rigging.

Zia, 78, was convicted of graft in 2018 and is now in ailing health at a hospital in Dhaka. BNP head Rahman is her son.