JERUSALEM (AP) -- Israeli warplanes unleashed airstrikes Wednesday against Syrian army targets in response to a roadside bombing in the Golan Heights that wounded four soldiers the day before, the military said.
In addition to the airstrikes, Defense Minister Moshe Yaalon warned Syrian President Bashar Assad that if he pursues a path harmful to Israel, he would "regret his actions."
There was no immediate word from Syrian authorities on the air raids.
But the Britain-based Syrian Observatory for Human Rights, which has a network of activists on the ground in Syria, said the Israeli air force targeted several "strategic posts of the Syrian army" near the villages of Kom and Nouriyeh. It said there were casualties among the Syrian military but gave no further details.
Tuesday's roadside bombing and Wednesday's strikes are the most significant escalation between Israel and Syria since the Syrian conflict began three years ago, though neither country has expressed interest in entering a war.
The military said the Israeli air force targeted a Syrian army training facility, an army headquarters and artillery batteries early on Wednesday. Israel also carried out artillery strikes against Syrian military targets shortly after Tuesday's bombing.
"There is a new situation on the Syrian frontier," said lawmaker Shaul Mofaz, a former defense chief, on Army Radio. "This will continue to be a serious challenge for us."
The Golan Heights bombing was the latest in a series of incidents along Israel's volatile frontiers. Last week, a roadside bomb exploded near an Israeli military patrol along the Lebanese border, causing no injuries. Earlier this month, the Israeli army said it killed two militants affiliated with Hezbollah -- the Lebanese militant group fighting in Syria alongside Assad's troops -- as they were trying to plant a bomb along the frontier.
Also, an Israeli airstrike last month reportedly targeted a suspected Hezbollah weapons convoy in southern Lebanon, though officials in Jerusalem never confirmed it. Hezbollah said it would retaliate for the airstrike, which killed a Hezbollah official overseeing the operation, according to a senior Lebanese security official speaking on condition of anonymity in line with regulations.
Israel's army stopped short of saying Hezbollah was behind Tuesday's bombing but Yaalon's statement put the blame on Assad's government.
"If (Assad) continues to cooperate with terrorists seeking to harm Israel, we will exact a heavy price from him, in a way that will cause him to regret his actions," Yaalon said.
Prime Minister Benjamin Netanyahu said Syria's army has assisted and participated in attacks on Israeli forces.
"Our policy is clear. We hurt those who hurt us," he said Wednesday.
Israel has said it will not allow sophisticated weapons to flow from Syria to the Iranian-supported Hezbollah, an ally of Assad and a top foe of the Jewish state. Israel and Hezbollah are bitter enemies and fought a month-long war in 2006.
Israel captured the Golan Heights from Syria in the 1967 Middle East war and later annexed the strategic area in a move that was not internationally recognized. Israeli forces have come under fire on several occasions since the uprising against Assad broke out in March 2011 and Israel has been carefully watching the fighting next door.
Though relations are hostile, the ruling Assad family has kept the frontier with the Israeli-held Golan quiet for most of the past four decades. Israel is concerned that an ouster of Assad could see power in Syria fall to Islamic militants there, particularly al-Qaida-linked groups, and further destabilize the region.
Fire from Syria, mostly errant, has occasionally hit Israeli border communities, damaging property and crops and sparking fires. Israel occasionally retaliates.
Despite the animosity, wounded Syrians have reached the frontier and Israeli soldiers have brought more than 750 of them into the country for treatment at Israeli hospitals.
Associated Press writer Bassem Mroue contributed to this report from Beirut.