The murders come less than one month after Natalya Estemirova, one of the best known activists in Chechnya and head of the rights group Memorial, was killed in similar circumstances.
Speaking to Al Jazeera, Tatiana Lokshina, the deputy head of Human Rights Watch in Moscow and someone who worked closely with Estemirova, said: "The perpetrators are not known but what is completely clear to us is that the climate for civic society workers in Chechnya today is absolutely intolerable.
"Unless this new double murder and the killing of Estemirova are properly and fully investigated, unless the perpetrators are brought to justice, one really cannot do independent reporting of human rights work in the region on the ground.
"It's incredibly important that the investigation into these killings is controlled by the Kremlin, done by investigators from the federal centre and not done by local servicemen, because the possibility of involvement of local officials in the killing cannot be excluded at all."
Sadulayeva's husband had previously been jailed for four years for links to banned armed groups and had married the charity head two months after leaving prison.
"This is just unimaginable. They killed a young woman, she was probably 25, and her husband, who was about the same age. They had just got married," said rights activist Ludmila Alexeyeva, of the Moscow Helsinki group.
Human rights activists have blamed the forces of Ramzan Kadyrov, the Kremlin-backed Chechen president, for the killing of Estemirova.
"The authorities in Chechnya have shown themselves to be very intolerant of criticism," Jane Buchanan of Human Rights Watch told Al Jazeera, shortly after the abduction of Sadulayeva and her husband.
"Natalia Estemirova had been herself threatened by Kadyrov in the past and he was not happy about the reporting she was doing exposing human rights abuses ... it's frankly a hostile environment to begin with.
"These are just outrageous crimes, the abduction and killing of Natalia Estemirova in a country that aspires to democratic standards is just appalling."
Kadyrov, condemned the killings as an "inhuman crime" and said he would take the investigation under his personal control.
"The person who committed this crime wanted to split our society, to destabilise the Chechen republic," he said.
Russia earlier this year ended a 10-year "counter-terrorism" operation in Chechnya, a mainly Muslim region riven by two separatist wars since the 1991 collapse of the Soviet Union.
However, Chechnya and other parts of the Russian Caucasus remain the site of a deadly insurgency led by Muslim fighters against the pro-Kremlin local authorities, who in turn have been accused of human rights abuses.
The reports of the killings came as a journalist for a local newspaper in Dagestan, a province in Russia's volatile south, was found shot dead on the outskirts of Makhachkala, the capital, according to Russian news agencies.
Malik Akhmedilov, who worked for Khakikat newspaper, was found with gun shot wounds to the stomach, a local interior ministry source said.
The murders come amid growing international pressure on Russia to end the apparent culture of impunity in which its activists are being killed after the unsolved killing of investigative journalist Anna Politkovskaya in 2006.