Extremist killer Tanveer Ahmed has sent a new message to his supporters from behind bars.

The 32-year-old is serving life for murdering Asad Shah last year because he believed the Glasgow shopkeeper was a “false prophet” who “disrespected Islam”.

However, has has been able to smuggle out audio messages to followers who support his actions in killing Mr Shah, a member of the Ahmadi faith persecuted in Ahmed’s native Pakistan.

Last week Ahmed used one such message, obtained by BBC Scotland, to back a major rally in Karachi attended by controversial preacher Khadim Hussain Rizvi, one of if his highest profile supporters.

Ahmed, a former Bradford taxi driver, said: “I have great restrictions imposed on me in prison but I am not failing to extend this invitation to you.”

He also said that he had been asked to give up his connections in Pakistan and claimed he had been warned off by what he called “agents of infidels”.

He said: “They threatened me and asked me to sever all contacts with these people.”

Previously Ahmed has used recordings from jail to attack Ahmadis and said he had no regrets over killing Mr Shah. said “I stood guard on the honour of Prophet Muhammad and I shall do it again if I shall get a chance.”

In another he says: “The penalty for those who insult the prophet: cut their heads from their bodies.”

At least one such recording, published on YouTube, have been taken down. Authorities are understood to be concerned that Ahmed may be seen as some kind of martyr for those with anti-Ahmadi prejudices. The latest message discovered by the BBC was posted on the Facebook page of Rizvi., whom Ahmed has described as a mentor. It had been viewed tens of thousands of time.

The Karachi rally was attended by people who made the same chants as Ahmed and his supporters made when he was jailed, for 27 years, after admitted his responsibility for Mr Shah’s murder. Crowds shouted “Labaik Ya Rasool Ullah” or “Here I am present, O Prophet”.

These expressions are often used by Pakistanis who want to maintain tough blasphemy laws, including those used to target minority Ahmadis.

Ahmed travelled to Glasgow to challenge Mr Shah after seeing the shopkeeper’s videos, in which he suggested he was a prophet. Some mainstream Muslims refuse to accept that Ahmadis share the same faith, arguing that members of the faith do not accept the word of the Prophet Mohammed as “final”. Some of Ahmed’s supporters see Mr Shah as a blasphemer. This crime, in Pakistan, can be punishable by death.

The Karachi rally was also attended by relatives of Mumtaz Qadri, an Islamist extremist who was hanged last year for the 2011 murder of a politician who had called for more relaxed blasphemy laws. Ahmed has been equated with Qadri by some in Pakistan.

The Scottish Prison Service does not comment on individual cases but is understood to be trying to get to the bottom of what Ahmed is saying to to whom in his messages. It is not clear how he is making audio recordings or getting them out of jail. A Ahmadi spokesman said: “It’s quite bizarre that the authorities haven’t taken steps in stopping the messages from coming from the prison.”