A British Royal Navy vessel, HMS Hurworth, is monitoring a Russian warship as it is passing through the English Channel in an exercise that usually lasts about 48 hours, the Navy says.

The Portsmouth-based minehunter, which is the fourth UK ship required to observe Russian movements around Britain in the last two months, is tracking Russian frigate Admiral Makarov on Wednesday.

According to the Ministry of Defense, patrol ship HMS Mersey, destroyer HMS Diamond and frigate Montrose had all been involved in observation activities during the past two months.

Earlier in August, HMS Diamond was sent to monitor two Russian warships, and in January, Royal Navy frigate HMS Westminster monitored four Russian vessels as they passed close to British waters.

The ministry, however, declined to comment on the exact number of Russian ships passing the UK.

Back in May, the head of the Royal Navy, First Sea Lord Admiral Sir Philip Jones, said that the UK was facing “significantly emboldened Russian Naval activity, which is continually testing our resolve.”

Official figures released in May showed that the Royal Navy intercepted Russian vessels on 33 occasions in 2017, compared to only one such mission in 2010.

The UK has ordered its military forces to respond to Russian military activity near its territories on more than 160 occasions over the past seven years.

In June 2016, Russia poked fun at the UK’s intercept of one of its submarines, saying it was surprised that the Royal Navy needed NATO’s help in tracking a submarine travelling at slow speeds “in surface position.”

Russia’s Stary Oskol submarine was first detected in the North Sea by NATO ships on June 7 the same year, and was then escorted by Britain’s frigate HMS Kent past the Strait of Dover the following day.