Lebanese Parliament Speaker Nabih Berri said Wednesday there were growing concerns about "sectarian strife" in Lebanon.
Lebanon's political structure is divided along religious lines. Those divisions have been strained by the role Shiite movement Hezbollah has played in Syria's civil war.
Hezbollah says it is fighting alongside pro-government forces in Syria to protect Lebanon from Syrian rebel groups, some of which are aligned with al-Qaida. Conflict has erupted, however, between pro- and anti-Syria elements near Lebanese-Syrian border.
Berri was quoted by the official National News Agency as calling "for doubling efforts to put an end to such attempts that threaten [to destabilize] the country."
U.N. High Commissioner for Refugees Antonio Guterres said from Beirut the refugee crisis was compounding the issue for Lebanon. He said Lebanon is on pace to host more than 1 million Syrian refugees by the end of the year.
Guterres said the threat of spillover from the Syrian war "is now becoming a harsh reality" for countries like Lebanon.
"The international community must overcome its divisions and come together to stop the fighting if we want to prevent the flames of war from spreading across the Middle East," he said in a statement.