Bangladesh goes to the polls in a week for its first contested general election in a decade, amid growing international concern at a process that critics say is stacked in favour of the ruling party.

The vote on 30 December will pit the incumbent Awami League of prime minister Sheikh Hasina against an opposition alliance led by the Bangladesh Nationalist Party (BNP), which boycotted the last election in 2014.

Candidates and activists for the opposition say they have faced attacks from pro-government thugs and harassment from the police. The BNP’s leader, former prime minister Khaleda Zia, is in jail on corruption charges that supporters say are politically motivated, and was handed a new seven-year term in November.

Asked by a journalist if he was aware of the issues in Bangladesh, where “a fair and credible election is beyond imagination”, a spokesperson for UN secretary-general Antonio Guterres said the UN was “following the situation closely”.

“It is very important as a matter of principle that anywhere there are elections, that they be conducted freely and fairly, and that the space be given for people to express themselves,” he said.

On Friday, Facebook and Twitter said they had shut down around 30 accounts that had been spreading fake news against the Bangladeshi opposition, some of which appeared to be linked to government figures.

The accounts included Facebook pages designed to mimic legitimate news outlets, among them the BBC. False stories included accounts of deep divisions within the BNP’s organisational structure, and a made-up tale about Ms Zia firing the party’s general secretary in a videotaped message from prison.

Nathaniel Gleicher, Facebook’s head of cybersecurity policy, told the Associated Press the people who created and managed the fake news sites were “associated with the government”, declining to provide further detail.

Twitter, in a statement posted on the social media site, said it was suspending 15 accounts “for engaging in coordinated platform manipulation”, and that they “may have ties to state-sponsored actors”.

Politics in Bangladesh has been dominated for years by the rivalry between Ms Hasina’s centre-left, socially and economically liberal Awami League and the more right-wing BNP with Ms Zia at its helm.

The last 10 years under the Awami League have been characterised by increasing authoritarianism, with harsh crackdowns on protest and several arrests for online posts critical of the government, including a prominent photographer released last month after more than 100 days in prison.

At the same time, the country has been held up as an example in the region for its remarkable economic growth, consistently achieving between 7 and 8 per cent annual rises in GDP and historic lows for poverty rates.

It has also achieved international plaudits for its role in supporting a million Rohingya Muslims who have fled neighbouring Myanmar. Domestically, Bangladeshis are proud their country has offered a safe haven but support the prompt repatriation of the refugees.

A lack of reliable polling ahead of the election means it is impossible to know whether voters will put economic growth or personal freedoms first when they get to the ballot box, said Dr Gareth Price, senior research fellow in Chatham House’s Asia-Pacific Programme.

If Ms Hasina wins the vote as expected, he told The Independent: “I am sure there will be some protests and I am sure they will be suppressed.

“It goes to the question of whether the average Bangladeshi thinks the present government has had 10 years and now it is time for a change, or whether they think the party is delivering well.

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“If there is desire for a change but the election result goes very much in favour of the ruling party, then it could be quite unpleasant.”

What’s certain is that it has been an ugly election campaign so far. The opposition said on Wednesday that 14 of its candidates had been arrested and 1,500 injured in attacks this month by ruling party workers, while police said at least five people have died in political clashes since 10 December.

Human Rights Watch has accused the ruling party and its supporters of creating an “atmosphere of fear” for opposition activists.

The government has denied involvement in any harassment. The violence also has not been one-way – two Awami League supporters have been killed in clashes, according to the AFP news agency.

Obaidul Quader, general secretary of the Awami League, told the agency his party did not tell its workers to attack opponents.