DHAKA - Bangladesh tightened security nationwide Sunday after a senior Jamaat-e-Islami (JI) leader was hanged for alleged war crimes during the 1971 conflict, a move that triggered anger among his opposition supporters but celebrations elsewhere.

Police said extra officers were deployed in the capital and other major cities hours after Mohammad Kamaruzzaman, the third most senior leader of the Jamaat-e-Islami party, was executed in a Dhaka prison late on Saturday. The 62-year-old was only the second person to be hanged for war crimes following his conviction in 2013 by a controversial tribunal, set up to investigate atrocities during the conflict. "We're alert against any bid to create anarchy or violence," a police spokesman told AFP. No major incidents had been reported as of early evening.

Jamaat, the largest Islamist party, called a nationwide "prayer day" for Sunday and a strike on Monday in protest at Kamaruzzaman's "heinous killing". The party branded it an act of "revenge and pre-planned murder" by the secular government. The hanging is expected to deepen a months-long political crisis that has seen the Islamists and the main opposition party launch nationwide protests to try to topple Prime Minister Sheikh Hasina. But the execution is unlikely to trigger the widespread deadly violence which followed the first war crimes execution in 2013 - also involving an Islamist.

Hundreds of Jamaat activists were killed that year when the party held a series of nationwide protests against trials of its leaders by the tribunal, which was established by Hasina's government.

Security forces have since rounded up thousands of Jamaat supporters in a massive crackdown on the unrest.

Bangladesh went ahead with the execution despite last-minute pleas by the United Nations, the European Union and human rights organisations. The UN has said the trial did not meet "fair international" standards.

Hundreds of secular activists and supporters of the trials gathered in central Dhaka on Saturday night to cheer and flash 'V for victory' signs over the death of a man they called a "war butcher".

Supporters of Hasina's ruling Awami League party also celebrated on Sunday with processions in Dhaka and other cities and by distributing sweets, police said. "It's an Eid day for us," a supporter in the northeastern city of Sylhet told television station Channel 24, referring to the major Muslim festival. After meeting his family one last time on Saturday, Kamaruzzaman was taken by specially trained convicts to a makeshift gallows for the execution about 10:30pm (1700 GMT).

His body was returned to his home village in the north where he was buried in a ceremony attended by about 100 people, local police chief Mazharul Karim told AFP. Scores of supporters visited his gravesite on Sunday to offer prayers, local online news portals said.

Prosecutors said Kamaruzzaman presided over the massacre of at least 120 unarmed farmers who were lined up and gunned down in the northern village of Sohagpur. Kamaruzzaman's lawyers argued that he was only 19 when the nine-month war broke out and was too young to have led any militia. Three women who lost their husbands testified against Kamaruzzaman in one of the most emotive of all the war crimes trials. "All 32 widows who are still alive are happy the notorious killer has been hanged.

Finally we got justice," said Mohammad Jalal Uddin, a Sohagpur farmer who lost seven members of his extended family in the killing.

At least five other Jamaat leaders have been sentenced to death. Their appeals are being heard in the Supreme Court. Jamaat and other critics say the war crimes trials are mainly aimed at silencing Hasina's opponents rather than delivering justice. Hasina's government says the trials - which lack any international oversight - are needed to heal the wounds of the conflict.