BEIRUT: President Michel Sleiman slammed Tuesday a Syrian airstrike on Lebanese territory as “unacceptable,” while Damascus denied any attack of that nature against its small neighbor.

Meanwhile, the opposition Future parliamentary bloc called on the Lebanese government to file a complaint at the United Nations and Arab League, while condemning what it described as “government negligence” in responding to the incident.

“President Michel Sleiman regarded the Syrian air bombardment of Lebanese territory as an unacceptable violation of Lebanese sovereignty,” a statement from the president’s office said.

Syrian jets and helicopters fired four rockets at targets inside Lebanon Monday, days after Damascus warned Beirut it would attack suspected rebel sites if incursions from across the border did not cease.

Sleiman’s statement comes a day after the United States confirmed Syrian aircraft attacked Lebanese territory, describing the incident as a “significant escalation in the violations of Lebanese sovereignty.” France, too, described it as a “new serious violation of Lebanon’s sovereignty.”

But Syria denied Monday the attack had taken place.

"Lebanese, Arab and international media circulated news about Syrian fighter jets dropping bombs inside Lebanese territory ... the [Syrian Foreign] Ministry affirms that there is absolutely no truth to this,” the state-run SANA quoted a high-ranking official at the Foreign Ministry as saying.

The source added that the ministry emphasized Syria’s respect for Lebanon’s sovereignty as well as its “commitment to the security and stability of sisterly Lebanon."

According to Sleiman’s office, the president tasked Foreign Minister Adnan Mansour with issuing a letter of complaint to Damascus “to prevent the recurrence of such operations.”

The two sites targeted in Monday’s aerial operation were the eastern border villages of Khirbet Youneen and Wadi al-Khayl, approximately 5 kilometers into Lebanese territory.

They are reportedly used for farming but have been suspected of being used as channels for smuggling arms and gunmen into Syria.

There were no casualties in the incident.

Tensions between the two neighbors spiked last week after Damascus warned Beirut it would attack rebels in Lebanon if incursions into Syrian territory continued.

In a letter sent to Lebanon’s Foreign Ministry last week, Damascus said Syrian troops were still exercising self-restraint by not striking “concentrations of armed gangs inside Lebanese territory in order to prevent them from crossing into Syrian territory.”

However, the letter warned: “this will not last indefinitely.”

Monday’s was the second Syrian aerial attack on Lebanese territory since the uprising against President Bashar Assad began.

In September 2012, a high-ranking security source told The Daily Star two Syrian warplanes bombed the farm fields of Khirbet Dawoud, Arsal, east Lebanon.

Also Tuesday, the Future parliamentary bloc called on the Cabinet to file a complaint at the Cairo-based Arab League and inform the U.N. and Arab states of the Syrian army violation.

“It is now necessary to lodge a complaint to the Arab League and inform the United Nations officially of this violation as well as a letter that contains facts and the violations of the Syrian regime's army to all Arab presidents and kings,” the bloc said in a statement following its weekly meeting.

It also voiced surprise over what it described as “government negligence” in taking the necessary measures to condemn and act upon the violation.

The opposition bloc also criticized the Defense Ministry, saying it had failed to provide citizens accurate information about the incident.

The bloc, headed by Sidon MP Fouad Siniora, however did praise the president’s statement for defending the country’s “national dignity and sovereignty.” - With additional reporting by Dana Khraiche