Sheikh Hasina was Sunday elected virtually unopposed from the Gopalganj-3 constituency as she won by a landslide, bagging 229,539 votes while her main BNP opponent could manage just 123.
The Election Commission officially announced Hasina's win in the evening.
Hasina is aiming for a record fourth term as prime minister with her Awami League opening up a big lead in early results following a tense vote.
She did not face much competition from her rivals as Bangladesh Nationalist Party's S M Jilani secured only 123 votes, Islami Andolan Bangladesh candidate Maruf Sheikh got 71, while rest of the candidates received a mere 14 votes.
According to the EC, a total of 229,747 votes were cast.
Bangladesh opposition alliance rejects polls, demands fresh vote
Facing imminent defeat, Bangladesh's opposition NUF alliance, with jailed ex-premier Khaleda Zia's BNP as its key partner, on Sunday rejected the outcome of the general election and demanded fresh polls under a neutral caretaker government.
The National Unity Front (NUF) is a coalition of parties including the main opposition Bangladesh Nationalist Party (BNP), Gono Forum, Jatiya Samajtantrik Dal-JSD, Nagorik Oikya and Krishak Sramik Janata League.
"We reject the results and demand a new election under a neutral government," NUF convenor Kamal Hossain, who heads the Gono Forum party, told a media conference.
His comments came after early trends and results suggested a landslide victory for Prime Minister Sheikh Hasina's ruling Awami League-led Grand Alliance.
"We ask that you cancel this election right away," Hossain urged the election commission claiming "we have reports that fraudulence took place in almost all centres".
BNP secretary general Mirza Fakhrul Islam Alamgir, who steered the party in Zia's absence and won from his northeastern constituency, described the polls as a "cruel farce".
"This has caused long-term damage to the country...the nation has incurred huge damage," he said.
A total of 47 opposition candidates boycotted Sunday's polls as voting was underway but Alamgir said they had stayed out due to personal reasons.
Several foreign observers, including from India, earlier said polls were going smoothly as they saw no anomalies in polling centres they had visited.
The Awami League, however, acknowledged that the polls were marred by violence at places but said 10 of its activists were also killed in opposition attacks as the clashes claimed 17 lives.