Bangladesh has executed head of the banned Jamaat-e-Islami party Motiur Rahman Nizami for war crimes committed during the 1971 war of independence to break away from Pakistan, the country's law minister said.

Nizami was hanged at Dhaka Central jail at one minute past midnight local time on Wednesday after the Supreme Court rejected his final plea against a death sentence imposed by a special tribunal for genocide, rape and orchestrating the massacre of top intellectuals during the war.

Thousands of extra police and border guards were deployed in the capital Dhaka and other major cities to tighten security as Jamaat-e-Islami called for a nationwide strike on Thursday in protest of the execution.

Previous similar judgments and executions have triggered violence that killed around 200 people, mainly Jamaat activists and police.

Al Jazeera's Tanvir Chowdhury, reporting from Dhaka, said the situation was still calm in the capital by Wednesday and there were no reports of violence in other cities.

"Unlike the last few years, Jamaat has not been able to materialise any kind of protest on the streets," he said, adding that this was mainly due to heavy-handed tactics used by the security forces.

"Jamaat supporters are not allowed to gather anywhere. Many of the leaders are behind the bars or on the run," he said.

"Human rights groups have criticised the government for extrajudicial killings and enforced disappearances. So, it is hard for them to gather anywhere. We will see what will come out of Jamaat's call for a 24-hour strike tomorrow from 6am."

Jamaat-e-Islami denies that its leaders committed any atrocities. Calling Nizami a "martyr", it said he was deprived of justice and made a victim of a political vendetta. Nizami had been in prison since 2010.

'False allegations'

A senior Jamaat-e-Islami leader based abroad told Al Jazeera that Nizami was a supporter of Pakistan in 1971 but "all other allegations of killing, murder and rape are not correct. The tribunal has miserably failed to prove any of those allegations."

He said Jamaat leaders inside Bangladesh were not giving interviews because their phones were tapped and their families were harassed if they spoke to media.

"Not only leaders, thousands of middle-ranking and ordinary Jamaat workers have been forced to flee their homes due to police repression or harassment. They are refugees in their own country due the vindictive nature of this government," he said.

"Their agenda is to wipe out Islam gradually and whoever they think opposes their policies is being targeted."

Five opposition politicians, including four Jamaat-e-Islami leaders, have been executed since late 2013 after being convicted by the tribunal.

International human rights groups say the tribunal's procedures fall short of international standards - an accusation the government denies.

According to Phil Robertson, the deputy director of the Asia division at the Human Rights Watch, the trial was neither free nor fair as the court was cutting corners on fair trial standards.

“For example, Nizami was allowed to have only four defence witnesses as a man fighting for his life. And the court did allow defence to challenge the inconsistencies in the testimonies of prosecution witnesses," he told Al Jazeera from Bangkok.

"Finally, we have seen a significant problem in all of these war crimes trials, where the presiding judge was having ongoing discussions about judicial strategy with external consultants and prosecutors in a way that raises concerns about the independence of the panel."

David Bergman, an investigative journalist in Dhaka, told Al Jazeera that there was long-standing allegations against Nizami since the end of the war.

"So the fact that there was a trial in which he was accused of these crimes is not itself political," he said, while also noting rights groups' criticism of the trials.

"There are no doubts that many members of Jamaat-e-Islami are concerned about trials and executions targeting its members, and the party itself is subject to significant repression."

The war crimes tribunal set up by Prime Minister Sheikh Hasina in 2010 has sparked violence and drawn criticism from opposition politicians, including leaders of Jamaat-e-Islami, that it is victimising Hasina's political opponents.

According to the Bangladesh government, about three million people were killed and thousands of women were raped during the 1971 war in which some factions, including the Jamaat-e-Islami, opposed the break from what was then called West Pakistan.

The execution comes as the country suffers a surge in violence in which atheist bloggers, academics, religious minorities and foreign aid workers have been killed.

In April alone, five people, including a university teacher, two gay activists and a Hindu, were hacked to death.