Detectives investigating the murder of an exiled Pakistani politician who was ambushed on his way home from work have made a second arrest.

Dr Imran Farooq was stabbed several times and bludgeoned with a house brick in Edgware, north London, four years ago but his killers have never been caught.

Two Pakistani men - Moshin Ali Syed, 29, and Muhammad Kashif Khan Kamran, 35 - are both wanted over the murder, which involved four attackers.

Officers from Scotland Yard arrested a 30-year-old in Waltham Forest, north-east London, today and are searching his home while he is questioned at a police station in central London.

This follows the arrest in June last year of a 52-year-old man, who had flown in to Heathrow Airport from Canada, on suspicion of conspiracy to murder. He is now on police bail until October.

Dr Farooq was a prominent member of the Pakistani political party MQM (Muttahida Qaumi Movement) and had been living in exile in the UK for more than a decade when he died.

In the weeks before his death he had been trying to raise his own political profile and had set up a Facebook page.

Police believe he was attacked by up to four men who had been seen near his house in Green Lane at various times, apparently watching him.

Dr Farooq died from stab wounds and head injuries. A £20,000 reward is available for information leading to the prosecution of his killers.

Anyone with information can call police on 020 7230 2717, or to remain anonymous contact Crimestoppers on 0800 555111.