Four British Islamists inspired by a former al-Qaeda leader admitted in court on Wednesday to plotting to blow up the London Stock Exchange in 2010.

The men belonged to a group of fundamentalists who plotted a spate of mail bomb attacks during the run-up to Christmas that year and discussed launching a "Mumbai-style" atrocity, Woolwich Crown Court in London heard.

Mohammed Chowdhury, 21, and Shah Rahman, 28, both from London, admitted preparing for acts of terrorism by planning to plant an improvised explosive device (IED) in the toilets of the London Stock Exchange.

Brothers Gurukanth Desai, 30, and Abdul Miah, 25, both from Cardiff in Wales, admitted the same count.

Five others, four from the central city of Stoke and another from Cardiff in Wales, also admitted involvement in the group.

Police seized a hand-written target list that included the mayor of London, two rabbis and the US embassy during the arrests.

Although they were not members of al-Qaeda, prosecutors said they were inspired by the terror network and specifically Anwar al-Awlaqi, a suspected leader of the group in Yemen who was killed in September in what is thought to have been a US drone strike.

The nine defendants "were implementing the published strategy of AQAP" (al-Qaeda in the Arabian Peninsula, the group's deadliest global branch), said prosecution lawyer Andrew Edis.

The group, who met because of their membership of various extremist Islamic groups, had originally challenged the charges against them and were due to stand trial, but at the 11th hour they changed their pleas to guilty.

They will be sentenced next week.