ISTANBUL -- One day after winning blanket authority to send forces into Syria, Turkey’s prime minister warned Friday that his country is “not far from war” and said that it would be a “deadly mistake” for the Syrian government to test Turkey’s will.

Prime Minister Recep Tayyip Erdogan made the comments as the Turkish military fired shells into Syria for the third straight day – retaliation for a mortar shell that landed just inside Turkish territory in Hatay province, according to the provincial governor.

Until Wednesday, when a Syrian shell killed five civilians in the border town of Akcakale, several hundred miles to the east, Turkey had avoided responding to what have appeared to be errant shells fired into Turkish territory by Syrian troops battling rebel forces for control of crossing points.

But after the five deaths Wednesday, Turkey appears to be retaliating for any Syrian shell that lands inside Turkey. On Thursday, a Syrian shell landed near the border in the town of Altinozou, causing no injuries but sparking a Turkish response. There were also no reports of Turkish injuries in the Friday shelling.

Turkish media reported, however, that at least seven Syrian soldiers were killed in Turkish shelling Wednesday and Thursday and a temporary Syrian military base was destroyed. It was unknown whether Syrian troops suffered casualties Friday from the Turkish shelling.

Two Turkish media outlets reported that the government of Syrian President Bashar Assad had taken steps to avoid further border clashes with Turkey, ordering the Syrian air force not to send fixed-wing combat aircraft or helicopters within six miles of the Turkish border.

Erdogan’s rhetoric left little doubt that the confrontation with Syria could flare into war, though he said he was not seeking a war.

“We have not, do not and will not fail to respond to any attempt to injure the dignity of our country,” Erdogan told a gathering in Istanbul. “I wish to state that we are not only not enthusiastic about war, we are also not far from war.”

Erdogan reminded his audience that Turkey, “when necessary,” has participated in inter-continental wars previously and quoted an adage: “Be ready for war if you want peace and goodness.”

“Anyone trying to test Turkey’s capacity for determination . . . would be making a deadly mistake,” he said. “We are not bluffing. We are not dealing in hollow statements.”

Erdogan, once an Assad ally, denounced what he called the Syrian government’s “state terror,” describing it as a “mentality that attacks its own people, does not value its own cities, its own cultural heritage, that bombs its own towns.”

“Such a brutal and merciless regime has long since lost its legitimacy, and any chance for its survival is completely lost,” he said. “God willing the Syrian people will be saved from this tyranny as soon as possible.”

Turkey has long supported the rebels seeking to topple Assad but has failed to win international support for opening a so-called humanitarian corridor into Syria that would allow Assad opponents to operate in a safe zone, free of concerns of attacks by forces loyal to the government. Its new aggressiveness, however, could have that impact, at least in a six-mile-wide strip along the Turkish border.