ANKARA (AFP) ― Tensions between Turkey and Syria rose Sunday, as Ankara said it scrambled fighter jets after Syrian helicopters flew close to the border, underlining the mistrust between the neighbors after the downing of a Turkish plane last month.

Prime Minister Recep Tayyip Erdogan insisted Sunday that a jet fighter shot down by Syria last month was in international airspace, dismissing a U.S. newspaper report that it was downed inside Syria as untrue.

Erdogan waded into the row at a meeting of his AKP party, saying that the Wall Street Journal had “unfortunately published a story which is not true.”

The comments follow a report Saturday in the newspaper citing US intelligence that claimed the plane was “most likely hit by shore-based anti-aircraft guns while it was inside Syrian airspace.”

Turkey has repeatedly said its F-4 Phantom warplane was downed without warning in international airspace on June 22, although it admitted that it had violated Syria’s airspace for a short time and “by mistake.”

The Turkish military gave further details in a statement Sunday, saying the plane had been inside Syrian airspace “for about five minutes.”

“We see no indication that it was shot down by a surface-to-air missile” as Turkey says, an unnamed senior U.S. defense official was quoted as telling the newspaper.

Meanwhile four F-16 warplanes took off on Saturday from Incirlik airbase after Syrian helicopters flew four 6.5 kilometers closer to the border than is normal, the army said in a statement.

Two more F-16 jets scrambled from a base in Batman after one helicopter approached the border in the south of Mardin province.

There were three incidents but there had been no violation of Turkish airspace, the army said.

Erdogan, speaking in the central Anatolian province of Kayseri, tied the publication of the article to the upcoming presidential election in the United States.

“The election is looming there and this newspaper is acting on behalf of a political movement. This is an attitude adopted against President (Barack) Obama,” said Erdogan.

He called on the newspaper to identify its source if it was to be taken seriously.

The two countries have engaged in several shows of force since the shooting down of the F-4 warplane.

Turkey sent missile batteries, tanks and troops to the border as a “security corridor” about a week after the F-4 incident, while Syrian troops were reportedly massing near the Turkish border a day after the Turkish mobilization.

Erdogan has vowed that any hostile Syrian movement towards the border would be “treated as a military target,” hinting at a harsher retaliation for any future border violations.

The Turkish prime minister was once an ally of Syrian President Bashar al-Assad, but relations have broken down since the revolt erupted in Syria last year, sending more than 33,000 refugees across the border into Turkey.