Geneva - Increasing violence by a pro-government militia, including executions, abductions and torture, is threatening to destabilise crisis-wracked Burundi, the United Nations human rights chief warned on Tuesday."They could tip an already extremely tense situation over the edge," Zeid Ra'ad Al Hussein said in a statement.Around 40 people have died and scores more have been injured in protests that began when the country's president for the past decade, Pierre Nkurunziza, announced in late April he would bid for a third term.The opposition and rights groups say the president's third-term bid violates a constitutional two-term limit as well as a 2006 peace deal that ended a 13-year civil war.In such a tense environment, Zeid said his office was receiving "truly chilling" reports from Burundians who have fled the country about violations committed by a militia known as Imbonerakure attached to the pro-government movement.The militia has carried out summary executions, abductions, torture, beatings, death threats and other forms of intimidation, according to testimony gathered from 47 Burundian refugees in camps in Rwanda and the Democratic Republic of Congo, the statement said.Attacked and lootedA 19-year-old refugee from the southern Makamba province told UN officials his house was attacked and looted by Imbonerakure members and his father was stabbed to death because he refused to join the ruling part CNDD-FDD.Numerous refugees also said threats had been scrawled across the doors and walls of houses, with some saying they had seen houses marked with a cross, apparently to identify people to target or attack.Zeid expressed alarm at repeated allegations "that Imbonerakure members operate under instructions from the ruling party and with support of the national police and intelligence services, who provide them with weapons, vehicles and sometimes uniforms.""If these clams are even partly true, they indicate an extremely dangerous effort to escalate fear and tension," he warned."If state authorities are indeed colluding with a violent lawless militia in this manner, they are gambling with the country's future in the most reckless manner imaginable."Zeid insisted that "now more than ever it is essential the Burundian authorities show their commitment to peace by clearly disassociating themselves from their violent supporters and ensuring accountability for any crime or human rights violation they may have committed."While few violent acts have been committed by the opposition so far, he also urged opposition leaders to "make a huge effort" to rein in any possible violent elements in their midst."The last thing Burundi needs after a decade of gradual and largely successful peace-building is to be catapulted back into civil war because of a small number of people's ruthless determination to retain, or gain, power at any cost," he said.