The UN peacekeeping mission in South Sudan announced Wednesday it was deploying troops to the country's strife-torn south following an upsurge in violence by armed rebels against civilians and aid workers. 

The deployment of blue helmets to establish a new outpost in Central Equatoria follows attacks on humanitarian convoys this week that left two civilians dead, and a roadside ambush in the same region in late August that killed six vice-presidential bodyguards.

UN special envoy David Shearer said the peacekeepers would set up a base at Lobonok, some 110 kilometres (70 miles) southeast of the capital Juba, in a region witnessing a resurgence in violent clashes between rebel and government forces.

"This will enable us to provide a protective presence in the area," said Shearer, who heads the UN Mission in South Sudan (UNMISS).

The rise in violence has been blamed on the National Salvation Front (NAS), a rebel movement active in the wider Equatoria region led by former deputy army chief Thomas Cirillo.

NAS claimed responsibility for the deadly attack near Lobonok on the bodyguards of Vice President James Wani Igga. 

Igga, one of South Sudan's five vice presidents, was not in the convoy and unharmed.

Gunmen from the holdout rebel group were also believed responsible for an ambush Tuesday on a relief convoy in Central Equatoria that left two civilians dead and four injured, and similar attacks that saw vehicles torched and people shot in recent days. 

NAS refused to be part of a 2018 peace deal between the government and other armed opposition groups that ended five years of fighting that left nearly 400,000 people dead.

But in January this year, during talks mediated in Rome, the rebels did agree to cease fighting and allow aid to freely reach people in desperate need across the Equatoria region.

However, violence has intensified recently across the region, with NAS instructing its troops to be on "maximum readiness" and warning civilians to avoid major roads where clashes with government troops were likely.

Shearer said he was concerned by reports that NAS rebels were again moving about the Equatoria region. 

"This violence is causing huge tension in the area and putting the lives of civilians at risk," he said, urging all parties to respect past ceasefires they had signed.

Clashes between government forces and Cirillo's rebels have exacted a horrific toll on civilians in the Equatoria region. 

In a report issued last July, the UN said civilians had been deliberately targeted by troops on both sides in months of violent attacks on villages, with hundreds raped or murdered.