Estonian Prime Minister Kaja Kallas and British Ambassador to Estonia Ross Allen, left, fly back together from NATO exercises in southern Estonia, Wednesday, May 15, 2024. Both the U.K. and Estonia recently announced arrests of people suspected of organizing sabotage operations on behalf of Russia. (AP Photo/Hendrik Osula)
Estonian Prime Minister Kaja Kallas, center, speaks to Brig. Charles Harris, commander of British forces in Estonia, left, and Ross Allen, British ambassador to Estonia, at an undisclosed location in Estonia on Wednesday, May 15, 2024. Kallas was visiting the country's largest defense exercises. (AP Photo/Hendrik Osula)
A British Chinook helicopter waits to take senior Estonian officials back to the capital of Tallinn after they watched military exercises in an undisclosed part of Estonia, Wednesday, May 15, 2024. Estonian, British and French forces took part in the exercises which were dubbed Spring Storm. (AP Photo/Hendrik Osula)
Estonian Prime Minister Kaja Kallas sits inside a British Chinook helicopter in Estonia, Wednesday, May 15, 2024. Kallas has called for a "serious" coordinated approach to deter and counter Russian hybrid attacks on European soil. (AP Photo/Hendrik Osula)
Estonia's capital of Tallinn is seen from a British Chinook helicopter on Wednesday, May 15, 2024. Estonia, occupied by the Soviets Union until 1991, joined NATO in 2004. (AP Photo/Hendrik Osula)
Former Estonian President Toomas Hendrik Ilves speaks during an interview with The Associated Press, in Tallinn, Estonia, Thursday, May 16, 2024. Ilves was president of Estonia from 2006-16, including while a large cyberattack carried out by Russia in 2007. Ilves suggested that if the West does not collectively deter Russia's hybrid threats, it will pay the price. (AP Photo/Sergei Grits)
Kusti Salm of Estonia's Defense Ministry, speaks during an interview with The Associated Press in Tallinn, Estonia, Thursday, May 16, 2024. Salm said Russia is carrying out attacks in Europe that include violence, sabotage, attacks on opposition figures and cyber threats. (AP Photo/Sergei Grits)
Jonatan Vseviov, secretary general at Estonia's Ministry of Foreign Affairs, poses for a photo in Tallinn, Estonia, Friday, May 17, 2024. Vseviov said Estonia is pushing for a European sanctions regime to be created to punish Russia for hybrid attacks. Estonia this year has arrested a university professor on charges of spying for Russia as well as 13 other people. (AP Photo/Emma Burrows)
Former Estonian President Toomas Hendrik Ilves speaks during an interview with The Associated Press, in Tallinn, Estonia, Thursday, May 16, 2024. Ilves was president of Estonia from 2006-16, including while a large cyberattack carried out by Russia in 2007. Ilves suggested that if the West does not collectively deter Russia's hybrid threats, it will pay the price. (AP Photo/Sergei Grits)
Former Estonian President Toomas Hendrik Ilves speaks during an interview with The Associated Press, in Tallinn, Estonia, Thursday, May 16, 2024. Ilves was president of Estonia from 2006-16, including while a large cyberattack carried out by Russia in 2007. Ilves suggested that if the West does not collectively deter Russia's hybrid threats, it will pay the price. (AP Photo/Sergei Grits)
Estonian Prime Minister Kaja Kallas, right, and British Ambassador to Estonia Ross Allen fly back from NATO exercises in southern Estonia, Wednesday, May 15, 2024. Both the U.K. and Estonia recently announced they have arrested people on suspicion of organizing sabotage operations on behalf of Russia. (AP Photo/Hendrik Osula)