Two men suspected of planning to kidnap and murder a female relative after she left the UK and renounced Islam have been arrested.
Mohammed Patman, 54, and Darya Khan Safi, 49, originally from Afghanistan, were arrested by officers from the NCA's Armed Operations Unit (AOU.
They were detained at their homes in London and Coventry on Wednesday 4 September.
The pair were wanted by the Slovakian authorities for conspiring to murder the 25-year-old woman.
The victim was living in Austria and working in Slovakia at a company she ran with her husband.
The National Firearms Threat Centre and the AOU initiated an investigation into the men in October last year after being alerted by the Slovakian authorities of the alleged murder plot.
AOU officers undertook surveillance on the two men as they prepared to make multiple trips to both Austria and Slovakia where they are believed to have carried out their own surveillance.
Read more from Yahoo News UK:
In pictures: Hurricane Dorian batters US east coast
Investigation launched after eggs thrown at nine-month-old baby
Boris Johnson appears to call Jeremy Corbyn a 'big girl's blouse'
Phone and internet records for the pair were obtained.
Officers allege they show the men discussing the potential murder plot including planning of events both at home and abroad.
Patman and Safi are being held on European Arrest Warrants and will now face extradition to Slovakia.
The men5 have been remanded in custody until their next appearance at Westminster Magistrates Court on Thursday 12 September.
NCA Senior Investigating Officer Matthew Perfect said: "Patman and Safi were sought by the Slovakian authorities for the extremely serious offence of preparing to commit first degree murder.
"Protecting the British public is a core part of the NCA's mission and these are two potentially violent individuals who will no longer pose a threat.
"They were arrested as a result of some excellent joint working between the NCA and our partners in Slovakia and throughout Europe.
“Such strong international cooperation is key in allowing us and our partners to pursue the most dangerous criminals across borders."