Venezuela lawmaker Serra's murder blamed on far right
Venezuelan President Nicolas Maduro has blamed "ultra-right" opposition groups in the country and in neighbouring Colombia for the murder of a governing party lawmaker.
Robert Serra, 27, and his partner Maria Herrera were found dead at their home on Wednesday night in Caracas.
Mr Maduro says the authorities are near to revealing the suspects' identities.
Mr Serra - one of Venezuela's youngest lawmakers - and Ms Herrera were reported to have been stabbed.
"Terrorist groups encouraged by sectors of Venezuela's ultra-right and Colombian paramilitary groups are behind this [effort] to bring violence to our country," President Maduro said.
Speaking at Mr Serra's funeral on Thursday, he said the investigation was "advanced", adding: "I think we're close to giving a strong blow to this criminal gang and assassins."
According to UN figures, Venezuela has the second highest peacetime murder rate in the world after Honduras.
Mr Maduro said the murders of Mr Serra and Ms Herrera were not random and that the authorities had detained suspects plotting to launch attacks from within other Venezuelan cities.
"In the course of this week... We have detained four different groups that came to attack our country's central cities, including Caracas, and fill them with violence," he said.
Mr Serra was a member of the National Assembly for the Socialist Party and well known for delivering passionate speeches.
Interior Minister Miguel Rodriguez Torres said that the murdered pair were "vilely killed here in their house... on the ground floor lay the woman and on the upper floor lay Robert Serra".
The killings came 10 days after President Maduro announced he would expand a plan to disarm civilians.
Last year, the president introduced tough penalties for illegal weapons possession, with sentences of up to 20 years in jail.
But despite these new laws, the perception of insecurity among Venezuelan citizens remains high, correspondents say.
Earlier this year, many took part in a series of mass anti-government protests demanding increased security as well as measures to improve the economy.