A Russian warship was escorted through the North Sea near U.K. waters by the British Royal Navy amid increasing tensions between the countries, officials said.
The HMS St Albans, with its 190 sailors aboard, escorted the Russian frigate Admiral Gorshkov on Monday through what British officials called "areas of national interest" on Christmas Day.
In addition, a Royal Navy helicopter was used to track other Russian vessels in the area.
The navy said there has been a recent surge in Russian vessels traveling near U.K. waters. Officials said that on Christmas Eve, a navy vessel was used to escort a Russian intelligence-gathering ship through the North Sea and the English Channel.
Defense Secretary Gavin Williamson said Britain wouldn't tolerate aggression.
"Britain will never be intimidated when it comes to protecting our country, our people and our national interests," he said in a statement on Tuesday.
In recent years, there has also been an increase in Russian fighter planes testing NATO and British air defenses, leading to jets being scrambled to keep those fighters away.
The incidents at sea follow a difficult visit to Moscow by Foreign Secretary Boris Johnson right before Christmas. Johnson and Russian Foreign Minister Sergey Lavrov disagreed on several issues, reflecting increasing tensions between Britain and Russia.
According to Sky News, Johnson accused Russia of meddling in Britain's internal affairs but said there were still areas in which the two countries could work together.
British officials warned this month that Russian ships might cut undersea internet cables in a bid to disrupt communications and commerce.
The Associated Press contributed to this report.