White House spokesman Jay Carney expressed regret for the loss of life in confrontations on Israel's frontiers with Syria, Lebanon and Gaza on Sunday but said Israel "has the right to prevent unauthorized crossing at its borders."

"We urge maximum restraint on all sides," Carney told reporters on Air Force One as President Barack Obama flew to Tennessee.

Israeli troops opened fire at three separate border locations to prevent crowds of demonstrators from crossing, killing at least 13 people.

Carney said the administration was "strongly opposed to the Syrian government's involvement in inciting yesterday's protests in the Golan Heights."

"Such behavior is unacceptable and does not serve as a distraction from the Syrian government's ongoing repression of demonstrators in its own country," he said.

Some Israeli officials suspect an Iranian hand in the attempted border breaches, with the help of Tehran's allies in the region: Syria, Hezbollah in Lebanon and Hamas in Gaza.

The Israeli delegation to the United Nations announced Monday that it would file a complaint to the UN Security Council against Syria and Lebanon regarding the Nakba Day border clashes.

The Lebanese delegation to the UN filed a complaint against Israel over the clashes, after the Lebanese army said that 10 people were killed and 112 were wounded in Maroun a-Ras when IDF troops opened fire on demonstrators trying to cross the border.

IDF sources said, however, that both Israeli and Lebanese forces opened fire to prevent demonstrators from crossing the border.

Israeli security forces were on alert for more violence on Monday, fearing that the events of the day prior may be serve as a model for additional violence aimed toward Israel and trigger further protests for Palestinian refugees.