A Russian SU-24M jet fighter prepares to take off from an airbase Hmeimim in Syria.

NATO’s secretary-general on Tuesday rejected Moscow’s claim that its military incursion into alliance airspace over Turkey wasn’t intentional or important, saying there were two separate incidents and “the violation lasted for a long time.”

Turkey’s military, meanwhile, said more of its jets patrolling the border with Syria were placed in a radar lock by Russian planes and surface-to-air missile systems.

In Syria, Russian warplanes reportedly continued pounding targets in the country, where the Kremlin has come to the aid of beleaguered ally President Bashar al-Assad.

NATO chief Jens Stoltenberg told a news conference in Brussels that recent breaches of Turkish airspace by Russian warplanes were “very serious”- even dangerous.

“It doesn’t look like an accident, and we’ve seen two of them over the weekend,” he added.

In a statement, NATO spokeswoman Carmen Romero said Stoltenberg later confirmed that NATO generals would be contacting their Russian counterparts about the violation of Turkish airspace.

Stoltenberg said NATO is expressly worried that such acts by the Russians could have unforeseen consequences.

“Incidents, accidents, may create dangerous situations,” Stoltenberg said. “And therefore it is also important to make sure that this doesn’t happen again.”

The latest Russian airstrikes in Syria, in cooperation with Syrian jets, struck targets in rural areas of the northern Aleppo province, targeting the towns of al-Bab and Deir Hafer, Syrian state TV reported, quoting a military official.

Both towns are controlled by the Islamic State of Iraq and Syria (ISIS) group. The official also said ISIS bases were targeted in Palmyra and surrounding areas in the central Homs province, destroying 20 vehicles, three arms depots and three rocket launchers.