Yameen Rasheed was stabbed in the stairwell of his apartment building in the capital, Male, on April 23.
The 29-year-old, who published a blog called the Daily Panic, was a well-known liberal who had often blogged about a rising tide of religious intolerance in the overwhelmingly Muslim nation in the Indian Ocean.
His father, Hussain, said his son had received numerous death threats from local Islamist zealots who were outraged by his opinions.
Maldives is an archipelago made up of 1,200 islands and its economy is based around the tourist industry. Most of the resorts are luxurious and cater for wealthy tourists from Europe, Australia and increasingly China.
The Maldives is portrayed by travel agents as a tropical paradise, but its politics have been turbulent in recent years.
Mohammed Nasheed was forced to resign as President in 2012 in what he claimed was a coup.
The following year he was narrowly defeated in an election by Abdulla Yameen Gayoom, the half-brother of Maumoon Abdul Gayoom, whose autocratic rule lasted 30 years until 2008. President Yameen has restricted opposition protests against his government.
In 2015 the president declared a state of emergency.
Six suspects are in custody and the authorities in the Maldives are getting forensic assistance from police forces in Europe and Japan.
"We strongly condemn the killing of Mr. Rasheed and we urge the government of the Maldives to take action now to promote and protect the rights of their people to express their views freely," a panel of UN experts, led by Special Rapporteur David Keys, said.
They said Rasheed was an outspoken critic of the government and wrote about alleged public corruption and human rights violations.
Their report said: "He had received numerous death threats, which he had reported to the police, who had apparently taken no action to protect him."
Lubna Zahir, a former Health Minister in the Maldives, tweeted: "I have never seen such a dedicated hero! Salute to Yameen Rasheed! You will live in all of us. May Allah grant you eternal paradise."
Rasheed is not the first journalist or campaigner to be killed in the Maldives.
In 2014, Ahmed Rilwan vanished after being abducted outside his apartment. He has never been seen since. He is believed to have been killed by an Islamist gang called Kuda Henveiru.
In response the Maldives government said it wanted to reiterate that President Gayoom had condemned Rasheed's murder "in the strongest terms."
On the Maldives Foreign Ministry's website they said: "The government has mobilized all of its resources to bring the perpetrators of this heinous crime to justice.
"The Maldives Police Service is giving top priority to the investigation of the Yameen Rasheed's murder."
They added: "The government of Maldives takes note of the interests that other governments and international agencies express on the case.
"The government also wishes to reiterate that the fundamental human rights of every citizen, as set out in the constitution of the Maldives, will be protected, and that the law enforcement authorities will always remain vigilant in protecting those rights."
The Maldives broke off diplomatic relations with Iran last year, in support of their fellow Sunni religionists in Saudi Arabia.