Massive protests have been staged in Managua against the re-election of Ortega and alleged vote fraud [AFP]

At least four people have been killed and 12 others injured in two post-election clashes between rival political groups in Nicaragua, police say.

One of those killed in a clash in the town of Siuna on Tuesday was the political secretary for President Daniel Ortega's Sandinista Party, two days after the presidential election that put Ortega back in office.

Fernando Borge, police commissioner, said seven police officers were among the injured in the fight between Sandinistas and members of the opposition Liberal Independent Party (PLI) in Siuna.

Borge also said on Wednesday that a 60-year-old woman and her two sons died late on Tuesday in the town of San Jose de Cusmapa.

He said those killed were caught in the midst of another violent confrontation between supporters of Ortega and backers of Fabio Gadea, the PLI presidential candidate who came second place in the vote.

Nicaragua's electoral council officially declared Ortega the winner on Tuesday, but complaints of voting irregularities by local and international groups have continued.

Following the results, a massive group of protesters took to the streets of Managua, the Nicaraguan capital, on Tuesday and Wednesday against the re-election of Ortega and alleged vote fraud.

Many demonstrators chanted: "Where is my vote, where is my vote?".

'Monstrous fraud'

Gadea called the electoral council's results "the manifestation of a monstrous fraud against the popular will".

A team from the European Union said on Tuesday that the vote was directed "by electoral authorities that were not completely independent nor impartial and who didn't fulfil their duty of transparency and of collaborating with all parties".

The team said the electoral council showed bias by allowing the people overseeing several polling places to come from only Ortega's Sandinista Party.

Ortega managed to seek re-election after the supreme court, dominated by his Sandinista appointees, overruled the two-term limits in 2009 set by the constitution.

Ortega also served as president from 1985 to 1990, after leading the Sandinista movement that overthrew the regime of Anastasio Somoza in 1979.