Ruling Awami League gained three more seats, including Jatiya Party stronghold Kurigram-2, in Thursday's by-elections.
BNP won two seats, Bogra-7 going to former speaker Mohammad Jamiruddin Sircar, and Bogra-6 to former law minister Moudud Ahmed.
JP's Roushan Ershad, wife of party chief HM Ershad, bagged his vacated seat in Rangpur-3.
AL's Abul Kalam Azad bagged Rangpur-6, while Md Zafar Ali won Kurigram-2. Nazmul Hasan Papon, son of president Md Zillur Rahman, won his father's Kishoreganj-6 seat.
Voter turnout was low. Election commissioner M Sohul Hussain estimated around 50-60 percent of the 1,842,000 registered voters cast their ballots in the six constituencies.
"Polling was peaceful in most areas," he said, though some disturbances were reported in Bogra.
7 seats vacated, Bagerhat-1 already filled
Six constituencies, two each, were vacated by prime minister Sheikh Hasina, Jatiya Party chairman HM Ershad and BNP chairperson Khaleda Zia when they took up their seats in parliament in january.
A seventh was vacated when Zillur Rahman was elected president last month.
The president vacated Kishoreganj-6, Hasina Rangpur-6 and Bagerhat-1, Ershad Rangpur-3 and Kurigram-2, and Khaleda Bogra-6 and 7.
Hasina's cousin Sheikh Helal Uddin was declared elected uncontested to Bagerhat-1 on Mar 17.
Clashes in Bogra
Seven people, two BNP and five Awami League activists, were reportedly injured at voting centres in Bogra-6 and 7 during Thursday's polling.
The supporters of the two parties clashed in five centres.
One Awami League activist was arrested on charges of violence and polling officer Shawkat Ali was suspended and detained on charges of campaigning for BNP's Jamiruddin Sircar in separate incidents.
CEC predicted low turnout
Chief election commissioner ATM Shamsul Huda predicted a low turnout, on the eve of the by-polls, compared to the Dec 29 general election.
"Voters may be a bit reluctant to go to polling stations, as this is the third occasion after parliamentary and Upazila elections, within a relatively short period," he said.
"Besides, farmers are busy with irrigation."
The CEC said the commission had taken all steps for free and fair election.
"I don't see any sign of elections possibly being rigged, there is no such scope," said Huda.
The EC appointed its own officials as returning officers for the first time in parliamentary polls.
In another rarity, the army and BDR were not being deployed to maintain election security in the wake February's mutiny.
Election officials said greater numbers of RAB, police and ansars were engaged, instead.
Election campaigning came to a stop on Tuesday midnight, bans were imposed on all vehicular movement from Wednesday midnight and a public holiday was declared in election areas to facilitate voting.