Acknowledging that he is not a "miracle-maker", the new UN chief Antonio Guterres has said that conflicts in the world are multiplying and interlinked and have triggered "a new phenomenon of global terrorism".

Speaking to his staff on his first day at the UN headquarters after taking over the world body's reins from Ban Ki-moon, 67-year-old Guterres said his election as the UN chief has generated a lot of expectations but he cautioned that there are no miracles.

"I think we should have no illusions. We are facing very challenging times. On one hand, we see everywhere in the world conflicts that multiply, that are interlinked, that also have triggered this new phenomenon of global terrorism, conflicts in which international humanitarian law is not respected, situations in which we see massive human rights violations, even refugee law is no longer as respected as it was few years ago," he said.

"I am sure I am not a miracle-maker. And the only way for us to be able to achieve our goals is to really work together as a team, and to be able to deserve to serve the noble values enshrined in the Charter (of the United Nations)," he said.

The former Portuguese prime minister said "nations are failing to recognise that there is a unifying factor in everything we do." 

"And that factor is people. People is undivided. And when we look at the different areas of action in the UN, we need to integrate them, because people integrate them on the receiving end," he said.

Guterres also stressed on the need to ensure that "we are able to reform the UN development system as Member States have asked us, and we need to try to get rid of this straight jacket of bureaucracy that makes our lives so difficult in many of the things we do.

"This requires a lot of effort from ourselves, but this also requires a lot of discussion and dialogue and mutual understanding with Member States and we need to overcome many of the divides that still exist within the organisation." 

Guterres called for teamwork, saying it is not enough to the "do the right thing, we need to earn the right to do the right thing." 

"It is important for us to recognise our achievements but we also need to recognise our shortcomings, to recognise our failures and where we are not able to deliver as we should," he said, outlining the multitude of challenges ranging from complex conflicts to global terrorism confronting the world.

Guterres' first day at UN Headquarters as Secretary General began with the laying of a wreath at the Memorial Wall.

Shortly after taking office two days ago, he made an appeal for peace. "Let us make 2017 a year in which we all citizens, governments, leaders strive to overcome our differences," Guterres said Sunday morning, urging people to share his New Year's resolution: "Let us resolve to put peace first."