TEHRAN, Young Journalists Club (YJC) - Lebanon's prime minister Saad Hariri resigned in a shock announcement broadcast from Riyadh on Saturday.
"It is essential that no new conflict erupt in the region," Guterres told reporters. "It would have devastating consequences."
"This is a matter of great concern to us. What we want is for peace to be preserved in Lebanon."
Guterres said he had been holding "very intense contacts" with Saudi Arabia, Lebanon, other countries in the region as well as governments with influence in the Middle East.
"We are indeed very worried and we hope that we won't see an escalation in the region that would have tragic consequences," said Guterres.
The UN chief spoke to Saudi Foreign Minister Adel al-Jubeir on Wednesday.
The head of Lebanon's Hezbollah movement said in Beirut that Hariri was "detained" by Saudi Arabia and prevented from returning to Lebanon.
Saudi Arabia and Kuwait have urged their citizens to leave Lebanon.