MOSCOW, March 19 (RIA Novosti) - Syrian warplanes delivered strikes on border area with Lebanon, allegedly targeting Syrian rebel positions on the Lebanese territory, Al Jazeera reported on Tuesday.

According to the agency, four missiles hit the Lebanese border town of Arsal, but no destruction or casualties were reported.

The US Department of State confirmed Syrian airstrikes on the border area and condemned them as a violation of the Lebanese sovereignty.

“This constitutes a significant escalation in the violations of Lebanese sovereignty that the Syrian regime has been guilty of. These kinds of violations of sovereignty are absolutely unacceptable,” US Department of State spokesman Victoria Nuland told a daily press briefing.

Last week, the Syrian Foreign Ministry officially warned the Lebanese Foreign Ministry that Damascus would strike militants' bases on Lebanese territory if Beirut failed to beef up security on their common border and prevent infiltration.

“The Syrian armed forces have showed restraint and have not delivered strikes on the bases of militant groups in Lebanon to prevent their intrusion into Syria, but that cannot last forever,” the Syrian ministry said in a statement on Thursday.

The Syrian Foreign Ministry also said that several groups of terrorists infiltrated into Syria from Lebanon early last week forcing the Syrian army to fight them back in several villages near the border.

Syria’s state-run news agency Sana claimed earlier this month that the United States military had made raids into Syria from Lebanon and Jordan for reconnaissance purposes and was preparing terrorist operations in support of Syrian rebels. The United States has consistently denied giving any military help to the Syrian opposition.