Former African National Congress intelligence operative suspected of circulating a document to the media and political parties detailing a plot to kill President Thabo Mbeki, appeared in the Pretoria Magistrate's Court yesterday but was not charged.

Police clamped down yesterday on information, with national director of communications Phuti Setati saying only that it involved a very "serious matter".

The man, best known as Bheki Jacobs and is believed to be the source of a document alleging irregularities in the arms deal, is to remain in custody at Pretoria's central police station until November 28 to allow for further investigation by police.

A problem facing the police is determining Jacobs' real identity.

Jacobs appeared in court under the name Uranin Vladimir Dzerzhinsky Solomons.

Although charges were not put to him, his charge sheet listed conspiracy or incitement relating to the Riotous Assembly Act, as well as fraud and contraventions of births and deaths registration, identity documents, and passports and travel documents.

Jacobs was arrested in Cape Town following a raid on properties belonging to him all over the country. Among other things computers were seized.

At the time of the raid, police said he had been arrested for passport irregularities, but the search warrant listed conspiracy to murder and crimen injuria as grounds for the search.

Sources close to the investigation said that Jacobs' arrest had to do with an anonymous document that has been circulated to politicians and the media.

The document appears to have mentioned a plot in which the president's diary committee and VIP protection were planning to kill Mbeki by tampering with the presidential jet.

They would then replace him with a chosen candidate.

The document is understood also to touch on the battle between Deputy President Jacob Zuma and prosecutions chief Bulelani Ngcuka, alleging that this has become the public face of battles between political forces.

It appears to detail a convoluted plot, based on a wide range of conspiracies, and claims that top-ranking South African politicians are embroiled in a bitter power struggle.

Key institutions are alleged to be involved in the wide-ranging conspiracy, from the French Intelligence to parliamentary committees.

It is believed that the document alleges that a number of efforts have been made to undermine the credibility of Mbeki, such as the leaking of minutes from the cabinet.

The commission of inquiry into allegations that Ngcuka was an apartheid spy and abused his office has taken a number of twists and turns since it was first convened in September.

Jacobs denied last week that he had written the document and said that he was being targeted by the National Intelligence Agency because of his suspected link to the earlier arms document.

Jacobs, who spent time in exile in the Soviet Union, has been known to use the names Vladimir Illich Solomons and Hassan Solomons, among others.

The presidency earlier distanced itself from speculation that Jacobs had advised Mbeki on security issues.

Presidential spokesman Bheki Khumalo has previously indicated that Jacobs had never worked for the president.

With acknowledgements to Chantelle Benjamin, Robyn Chalmers and the Business Day.