Prime Minister Sheikh Hasina’s ruling party won Bangladesh’s election with a large majority, the country’s Election Commission said early on Monday, giving Mrs. Hasina a third straight term following a vote that the opposition rejected as flawed.

At least 17 people were killed in Bangladesh in election-related violence on Sunday, according to the police, as voters went to the polls to decide an election tainted by widespread allegations of rigging by the government.

The win by Mrs. Hasina’s Awami League, which was reported by the secretary of the Election Commission Secretariat in a televised speech, would consolidate her decade-long rule over Bangladesh. Mrs. Hasina is credited with improving the economy and promoting development, but has also been accused of rampant human rights abuses, a crackdown on the news media and suppressing dissent — charges she denies.

The head of the opposition coalition, Kamal Hossain, said the alliance had asked the Election Commission to order a fresh vote under a neutral administration “as soon as possible,” alleging Sunday’s poll was unfair and that Mrs. Hasina’s government never granted her opponents a level playing field.