Five people have been killed and four injured in a clash between Venezuelan police and members of a pro-government militia, raising fears of a surge in political violence.

The incident began on Tuesday when a police special forces unit raided the headquarters of the Shield of the Revolution colectivo in downtown Caracas. The initial confrontation – in which one colectivo member was killed – led to an eight-hour standoff during which police and militia members exchanged shots around the high-rise building while helicopters hovered overhead. Three policemen were taken hostage by the group.

During a lull in the shooting, another militia leader, José Odreman, told reporters that his comrade had been shot dead in his sleep. Odreman, a former policeman, also warned that if anything were to happen to him, the responsibility would be in the hands of the justice minister, Miguel Rodríguez Torres.

“I lay full responsibility on you of what might happen to me. Enough comrades have been sacrificed”, Odreman said on camera addressing Rodriguez Torres.

Shortly afterwards, Odreman was shot dead. Photographs posted on social networks showed Odreman being held captive by security officers followed by videos where his dead body can be seen lying in a pool of blood.

The clash comes a week after the murder of a rising star in the country’s ruling United Socialist party (PSUV). Robert Serra, 27, became the youngest member of the country’s national assembly when he was elected in 2010, after gaining prominence organising counter-demonstrations against student protests in 2007. He and his partner, Maria Herrera, were found stabbed to death in their home on 1 September.

Speaking with reporters before his death, Odreman hinted that there was a link between the two incidents. Asked by journalists if the raid was somehow related to Serra’s death, Odreman replied: “mathematics doesn’t fail”.

José Gregorio Sierralta, the commander of the judicial police, and Rodriguez Torres both denied any link between the two incidents, describing Odreman as the leader of a gang which had been under investigation for mulitple murders.

Venezuela’s colectivos are civilian militia groups established to defend the Bolivarian revolution of the late president Hugo Chávez. They have been accused of harrassing opposition activists and played a prominent role in street fighting during a wave of anti-government protests earlier this year.

After Odreman’s death, a series of pictures appeared on social media showing the militia leader alongside high-ranking officials including the late Chavez, former vice-president José Vicente Rangel and President Nicolás Maduro’s wife, Cilia Flores.

Analysts fear confrontations between pro-government groups herald a fresh round of political violence in the highly polarised nation.

“Chavismo is a big de-centered movement that emphasises participation and defence of the revolution. That in itself would be difficult to control. But in the current situation the government does not have a clear monopoly of the means of lethal force and that makes this very dangerous”, said Prof David Smylde, a senior fellow at the Washington Office on Latin America.

Maduro and other high-ranking government officials have blamed Serra’s death on members of the opposition. Earlier this month, Rodriguez Torres accused the former Colombian president, Álvaro Uribe, of having links with Venezuelan opposition militants he alleged were planning a series of political assassinations, to create political turmoil.