A Russian fighter jet flew very close to a US surveillance aircraft over Syria, forcing it to go through the turbulent wake and putting the lives of the four American crew members in danger, US officials said.

The officials said the incident was a significant escalation in what has been a string of encounters between US and Russian aircraft in Syria in recent weeks. The intercept by the Russian Su-35 impeded the US crew’s ability to safely operate their MC-12 aircraft, the officials said, calling it a new level of unsafe behaviour that could result in an accident or loss of life.

In recent weeks, Russian fighter jets have repeatedly harassed US unmanned MQ-9 drones, but the latest incident raised alarms because it endangered American lives.

The officials, who spoke on condition of anonymity to discuss details of a military operation, would not say how close the Russian jet got to the US warplane. The MC-12, which is a twin-engine turboprop aircraft routinely used by special operations forces, was doing surveillance in support of operations against the Islamic State groups in Syria, the officials said.

On multiple occasions in the past two weeks, Russian fighter jets flew dangerously close to MQ-9 Reapers, setting off flares and forcing the drones to take evasive manoeuvres. US and Russian military officers communicate frequently over a deconfliction phone line during the encounters, protesting the other side’s actions.

The US is considering a number of military options to address the increasing Russian aggression in the skies over Syria, which complicated efforts to strike an Islamic State group leader earlier this month, according to a senior defence official. The US was eventually able to launch a strike and kill the militant.

The official, who also spoke on condition of anonymity to discuss military operations, declined to detail the options under consideration but said the US will not cede any territory and will continue to fly in the western part of the country on anti-Islamic State missions.

The Russian military activity, which has increased in frequency and aggression since March, stems from growing co-operation and co-ordination between Moscow, Tehran and the Syrian Government to try to pressure the US to leave Syria.

There are about 900 US forces in the country, and others move in and out to conduct missions targeting Islamic State group militants.