Four men have been charged with plotting a terror attack in London after allegedly swearing an oath of allegiance to Isis (Islamic State) and "retaining images" of police officers.

Tarik Hassane, 21, Suhaib Majeed, 20, Nyall Hamlett, 24, and Momen Motasim, 21, have all been charged with a variety of charges relating to intending to commit acts of terrorism.

A fifth man, Nathan Cuffy, 25, has also been charged with firearms offences in relation to the investigation.

Among the long list of allegations of preparing an act of terrorism, the four men are accused of conducting "hostile reconnaissance" of Shepherds Bush Police Station and White City Territorial Army Barracks using Google Maps and possessing a converted Baikal handgun along with six rounds of ammunition.

The group are also accused of viewing and retaining an image sent via Instagram of two Metropolitan police officers as well as two Metropolitan police community support officers.

The men are alleged to have "set up methods of secret communications" to plan an attack using mopeds for a possible drive-by shooting.

Following the men's arrest, the Association of Chief Police Officers (ACPO) sent a warning to every police force in the UK to be vigilant "for their own personal safety" as the threat towards police had "heightened".

It is also alleged they possessed extreme jihadist material, including articles with graphic images of the beheading of Steven Sotloff.

Cuffy, 25, has been charged with two firearms offences.

All five men are due to appear at Westminster Magistrates' Court.

Two others, a 20-year-old man and a 19-year-old woman, were released from custody following their arrest.