In what appears to be a further escalation in Turkey’s confrontation with Russia, reports say Russian ships entering the Bosporus Strait from both directions have been held up for hours before being allowed to transit the waterway. The escalation comes in the wake of Turkey downing a Russian aircraft in Syria on Nov. 24. Tensions have become further inflamed after a report by Turkish daily Zaman on Dec. 7 that a Russian warship sailed through the Bosporus on Sunday with a soldier holding a shoulder-fired surface-to-air missile on the deck of the ship. In response, Ankara summoned the Russian ambassador to the Turkish Foreign Ministry.

According to the Montreux Convention of 1936, the Bosporus is an international waterway under the control of Turkey, but there are very limited circumstances in which Turkey can block or even delay ships from passing through the strait. Despite this, Turkey seems to be going out of its way to make transit through the Bosporus more time consuming and, therefore, more expensive for the Russians. The cause of these delays is unclear. There are two possible situations in which Turkey could delay passage for certain ships. The country can claim that it is merely conducting a sanitary inspection, as stipulated by Article 2 of the convention. Alternatively, numerous other articles, including Articles 5 and 6, allow Turkey to inhibit passage through the Bosporus if the country is at war or threatened with the “imminent danger of war.”

At this point, Turkey has not given any justification but in this case the justification matters. If it is simply using a technicality as an excuse to delay Russian ships, then this could just be seen as mere harassment. But if Turkey were to claim it is in a near-war situation, this would be of course a justification and one that takes us to a very different place than we are now. That the country is taking this measure is interesting in itself, but how Turkey justifies its actions will be the most important outcome of this situation, if the reports of delays are accurate.

Meanwhile, Turkish news media has also been speculating that the government may bar Russian ships from the Bosporus. This would be an extremely damaging step for the Russians, as all trade from the south, as well as maritime support for Russian forces in Syria, must pass through the port. The Turks have not taken this step, which would technically be possible only in the event of a declared war. However, they are clearly indicating that they have no intention of de-escalating the situation and are actually prepared to intensify it. Clearly, the Russian-Turkish confrontation is not over and the possibility for further clashes cannot be ruled out.