The attack on former Ming Pao editor Kevin Lau was most likely ordered by a mastermind, whose capture would be a huge challenge to police, private investigators said.

They said the evidence so far showed the attackers were hitmen told to maim but not kill Lau.

It is also possible they got their orders through middlemen without knowing who ordered the hit.

Steve Vickers, the former head of the police's Criminal Intelligence Bureau who is now chief of business intelligence and risk consultancy SVA, believes the attack was clearly "preplanned and with full of criminal intent.''

He added: "Such attacks are predicated by surveillance of the target to get his movements and timing, such as where he has breakfast.''

Vickers said the motive remains murky, "but I would tend toward the view that it was some form of very serious warning; he has clearly angered a powerful group.''

When asked if it is difficult to trace the mastermind and why similar attacks had not yet been solved, Vickers said: "It is regrettable that the force has not made disruption of triad activity a priority over the past five years. Some groups have strong connections in the mainland and have become rich and powerful since the handover.

"Motives in this attack may include, but not limited to, the persons who were exposed in the British Virgin Islands company stories and to the rich and influential mainland persons recently."

University of Hong Kong department of social work and social administration associate professor Eric Chui Wing-hong, who has studied crime, also believes the attack was planned, but that it was hard to speculate on the motives.

"The attackers obviously knew which parts of the body to attack in order to cause severe bodily harm without killing him. If they intended to kill, they would not have targeted the neck, back and legs.''

Meanwhile, Ming Pao said it may use donations to increase the current reward of HK$ 1 million for the arrest of the attackers. Editorial director Cheung kin-bor, who is also a former chief editor, said staff will also compile all its sensitive reports _ political, economic and daily news, such as reports on illegal structures _ and cooperate with the police investigation.