U.S. Ambassador Nikki Haley says an emergency meeting of the United Nations Security Council has been called over the escalating situation between Russia and Ukraine, reported the Time. 

Haley tweeted that a meeting has been called for 11 a.m. Monday.

The Ukrainian navy says Russian ships fired on and seized two of its artillery ships Sunday in the Black Sea following an incident near Crimea, which Moscow annexed from Kiev in 2014. A tugboat was also seized, and two crew members were hurt.

Russia has blamed Ukraine for preparing and orchestrating “provocations.”

The incident sharply escalated tensions that have been growing between the two countries since Moscow annexed Crimea from Ukraine. Russia has since worked steadily to bolster its zone of control around the Crimean Peninsula.