A British warship escorted a Russian frigate on Christmas Day as it skirted British territorial waters, the UK's Defense Ministry said on Tuesday.

The UK's HMS St. Albans monitored the Russian warship Admiral Gorshkov in the North Sea, "keeping track of its activity in areas of national interest," the ministry said in a statement.

Read more: NATO chiefs warns of Russian submarine capability

On Sunday, HMS Tyne was deployed to track a "Russian intelligence-gathering ship." The defense ministry said it had observed an "upsurge in Russian units transiting UK waters."

Russia's latest maritime activity comes as relations between London and Moscow continue to deteriorate in the wake of Moscow's illegal annexation of the Crimean Peninsula from Ukraine in 2014.

'Destabilize European states'

During an official visit to Moscow, British Foreign Secretary Boris Johnson said London could not ignore Russia's interference in democratic processes across the globe alongside its involvement in a destabilizing conflict in eastern Ukraine.

"Our relations with Russia cannot be 'business as usual' whilst Russia continues to attempt to destabilize European states, including Ukraine," Johnson said.

British authorities have suggested that Russia may have meddled in the Brexit referendum, which witnessed a narrow majority vote in favor of a formal divorce from the EU.

Brexit negotiations: What are the key issues? Two phases EU leaders agreed to negotiating guidelines during a summit in April 2017 that divided the divorce talks into two phases. Phase I, in which both sides aimed to settle the basic terms of Britain's departure, started in July and ended with an agreement on "sufficient progress" in December. Officials are now holding Phase II negotiations on the post-Brexit relationship between Britain and the EU.

Brexit negotiations: What are the key issues? The "Brexit Bill" London agreed to a formula for calculating what it owes in its "divorce bill" to the EU in early December after months of haggling by British officials. The current EU budget expires in 2022 and EU officials have said the divorce bill will cover financial obligations Britain had committed to before triggering article 50. The final bill will reportedly total around £50 billion (€67 billion).

Brexit negotiations: What are the key issues? Citizens' rights Both sides agreed in early December that the 3 million EU citizens currently in Britain and the 1.1 million British citizens in the EU keep their residency rights after Brexit. British courts will have immediate jurisdiction over EU citizens living in Britain. But the EU's highest court, the ECJ, can hear cases until 2027 if British judges refer unclear cases to them.

Brexit negotiations: What are the key issues? The Irish border Britain and the EU also agreed in December that no border checks between the Republic of Ireland and Northern Ireland would return post-Brexit. How feasible the commitment will be is unclear, as Britain's commitment to leaving the EU Single Market and Customs Union makes it difficult to avoid customs checks at the Irish border.

Brexit negotiations: What are the key issues? Transition period Theresa May envisages a two-year transition period after March 2019. Both sides still have to hash out the details of the transition period in Phase II, including the exact end-date, whether new EU laws passed during the period will apply to Britain, and whether Britain can negotiate its own free trade deals. British officials hope to agree on the terms of the transition by March 2018.

Brexit negotiations: What are the key issues? Trade May has repeatedly said Britain will leave the European Single Market and the EU Customs Union. Leaving both could disrupt British-EU trade, but allow Britain to negotiate its own free trade deals and restrict EU migration — key demands by pro-Brexit politicians. London has said it wants to negotiate a new EU-UK trade deal during Phase II to minimize trade disruption before March 2019.

Brexit negotiations: What are the key issues? Immigration Britain has also vowed to restrict EU migration into Britain after Brexit. However, some British lawmakers are wary that a sharp drop in immigration could lead to shortfalls in key sectors, including health, social care and construction. The EU has warned that Single Market access is out of the question if London decides to restrict the ability of its citizens to live and work in Britain.

Brexit negotiations: What are the key issues? Security Recent terror attacks across Europe including a string in Britain underline both sides' support for continued security cooperation after March 2019. But access to EU institutions such as Europol and programs such as the European Arrest Warrant require compliance with EU laws. Whether Britain will still be compliant after it leaves is unclear. Author: Alexander Pearson



Deteriorating relations

Relations began to deteriorate in 2006, when Russia refused to extradite a Russian security official suspected of involvement in the murder of Kremlin critic and former spy Alexander Litvinenko.

Is NATO doing enough to pressure Russia over Ukraine?

However, they took a turn for the worst in 2014, when Russia staged a military intervention and conducted an internationally condemned referendum that resulted in the illegal annexation of the Crimean Peninsula.

Last month, British Prime Minister Theresa May accused Russia of "threatening the international world order on which we all depend."

British Foreign Minister Boris Johnson told reporters in Moscow that there is "abundant evidence" of Russia's meddling in Western democratic processes

ls/rc (AFP, Reuters)