Searches are being carried out by counter-terror police investigating the murder of Pakistani politician Imran Farooq, Scotland Yard said today.
Two residential addresses in north-west London are being examined and so far no arrests have been made.
Dr Farooq was stabbed to death outside his home in Edgware, north London in 2010 when he was ambushed on his way home from work.
He 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, Edgware, at various different times, apparently watching him.
Dr Farooq died from stab wounds and head injuries when he was attacked with knives and a house brick.
In the last three years investigators have interviewed eight people under caution and searched 10 addresses, but no one has ever been charged with the murder.
A £20,000 reward is available for information leading to the prosecution of Dr Farooq's killers.
Dr Imran Farooq was on his way home from work when he was attacked outside his home in Green Lane, Edgware shortly before 5.30pm on Thursday 16th September 2010.
A post-mortem gave his cause of death as multiple stab wounds and blunt trauma to the head.
A five and a half inch-bladed kitchen knife and a house brick used in the attack were recovered at the scene.
Detectives from the Met Police Counter Terrorism Command remain committed to finding those responsible.
They believe his murder would have required careful planning and would have required help from other people, some of whom may have provided assistance or information unwittingly.
They want to speak to anyone who was asked for information about Dr Farooq and his routine.
The Met Police has issued a fresh appeal for information as they try to solve the murder of Dr Imran Farooq in Edgware in September 2010. Dr Farooq was a Pakistani politician and detectives believe he was planning to renew his political career before he was killed.
They are asking anyone who was in contact with him about his plans to get in touch with them so they can build up a picture of his political life.
A reward of up £20,000 has been offered for anyone providing information that leads to Dr Farooq's killer. The Met believes his murder was planned and several people may have been involved.