The United Kingdom has tagged Russia as the biggest threat to its national security alongside the Islamic State (ISIS) and the Ebola virus.

In its latest list of potential threats, Britain cited Russia's increasing aggression, in particular President Vladimir Putin's "willingness to display force,'' as having unnerved its defence security network, the Daily Express reported.

Global terrorism, radicalisation by the ISIS and other extreme groups, migration crisis and global health threats like Ebola also made it to the list.

The new roster of potential threats was put together by the British government after a major security review that the U.K. performs every five years. It is expected to become a key part of the U.K.'s National Security Strategy which Prime Minister David Cameron is expected to announce on Nov. 23, according to The Sunday Times.

According to the report, Russia made it to the top spot due to the Ukrainian crisis. The crash of a Russian Airbus 321 jet in Egypt's Sinai Peninsula also reportedly added to British security concerns.

"Russia's actions in Ukraine have introduced question marks over the role and future of NATO operations in neighbouring countries and re-awakened the threat posed by Russia to states in Eastern Europe and the Baltic, some of which are NATO and/or EU member states,'' the Strategy document said, according to the Times.

Moscow's increased involvement in the Middle East, such as Russian airstrikes against terror targets in Syria, renewed flights by strategic bombers, and submarine activity in the north Atlantic have also alarmed the U.K. leadership.

In addition, the country's increasing isolation in international politics, increased military spending and apparent willingness to display force in the face of universal condemnation "suggest the next five years could well see an escalation of the Russian threat to the security of Western Europe.''

In the previous security strategy released in 2010, Russia was not mentioned as a threat, The Daily Mail noted.

Another country that has unnerved U.K. authorities is China, which it claimed is responsible for "authoritarianism and persistent human rights abuses.'' The strategy likewise cited as concerns in the escalating tensions in the South China Sea and China's closer relations with Russia.

The ongoing migration crisis in Europe as well as climate change and organised crime; the global increase in religious fundamentalism and intolerance across religions are also among those considered major concerns in Britain.

"In particular Islamic separatists and fundamentalists are now seen a serious threat in destabilised parts of the world,'' said the report.

The other danger that made it to the list is the rampant health epidemic such as the Ebola crisis this year, which killed more than 11,000 people worldwide mostly in Guinea, Liberia and Sierra Leone in South Africa.

As of August 2015, there were 28,041 Ebola cases reported globally, according to the World Health Organisation (WHO).