LONDON (Reuters) - The Royal Navy said one of its vessels was monitoring a Russian warship in the English Channel, the fourth UK ship required to observe Russian movements around Britain in the last two months.

HMS Hurworth, a Portsmouth-based minehunter, is keeping watch over Russian frigate Admiral Makarov as it passes through the Channel on Wednesday, in a monitoring exercise that usually lasts about 48 hours.

The Ministry of Defence declined to comment on the exact number of Russian ships passing the UK but said that over the past two months patrol ship HMS Mersey, destroyer HMS Diamond and frigate Montrose had all been involved in observation activities.

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

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