NEW DELHI: Syria and Lebanon agreed to a ceasefire late Monday after Syrian forces loyal to the new government in Damascus clashed with the Lebanese military on the countries’ shared border, as simmering tensions over key smuggling routes — long used by Hezbollah militants — erupted overnight, igniting a potential new flash point in a region roiled by war.

The agreement to halt the fighting was made in a phone call between Lebanese Defense Minister Michel Menassa and his Syrian counterpart, Murhaf Abu Qasra, Lebanon’s Defense Ministry said in a statement. The two sides would continue to communicate through their military intelligence agencies to “prevent the deterioration of the situation” and “avoid innocent civilian casualties,” the statement said.

The violence first broke out on Sunday, in the area where northern Lebanon meets western Syria, after what Syrian authorities said was a deadly ambush by Hezbollah gunmen against three Syrian soldiers. Syria’s new army, led by former rebels, launched rockets and artillery into Lebanon in response, sending residents fleeing and drawing fire from the Lebanese military and other armed groups.

Lebanese officials said Monday that the three people who were killed were smugglers, but it was not clear who killed them. Their bodies were returned to Syria through the Red Cross, Lebanese Information Minister Paul Morcos said.

“What is happening on the eastern and northeastern borders is unacceptable and cannot continue,” Lebanese President Joseph Aoun said Monday in a statement, before the ceasefire. “I have given instructions to the Lebanese army to respond to the sources of fire.”

Tensions across the countries’ porous border have been brewing since Syria’s new Islamist leaders ousted Bashar al-Assad, a key ally of both Hezbollah and its patron, Iran, in December. The frontier has long served as a critical smuggling and supply route for Hezbollah, a once powerful force whose influence has diminished since fighting a bruising war with Israel in the fall.

Syria’s new government has promised to crack down on Iran using its soil as part of a network for smuggling arms and cash to its proxy forces. It is also working to show it can control areas of the country traditionally supportive of the previous regime, following a wave of deadly sectarian violence along Syria’s coast earlier this month.

Syrian state media said that the three soldiers were ambushed near the Zeita Dam, west of Homs, and were killed on the spot after being taken to Lebanese territory. Hezbollah denied the accusations, saying in a statement it “has no connection to any events taking place within Syrian territory.”

Lebanese media reported that three armed men entered Lebanon first, resulting in clashes with local tribespeople who believed they were under attack. Many of the tribes in northeastern Lebanon are loyal to Hezbollah and have sporadically clashed with Syrian forces trying to disrupt Hezbollah’s supply lines.

The shelling from Syria on Monday centered on two border villages in Lebanon: al-Qasr, less than a mile from the Syrian border, and Hawsh al-Sayyid Ali, which straddles the frontier.

“They are bombing randomly against civilians in al-Qasr and other border villages,” resident Mohamad Jaffar, 55, said of Syrian forces, adding that the shelling had already caused significant damage. The Lebanese military, he said, was firing back from Ras Baalbek, about 18 miles south of al-Qasr.

“Military units responded to the sources of fire with appropriate weapons and are working to reinforce their defensive positions to stop attacks on Lebanese territory,” the Lebanese army said in a statement. It said that contacts between the Lebanese army command and Syrian authorities were being facilitated to restore calm. In Beirut, the cabinet said it would also raise its level of coordination with the Syrian government and form a committee to propose measures to tighten security on the border.