The four assailants were all wearing black caps at the time of the attack, according to police, although the sketches only showed one wearing a cap. Police said the third man was about 30, 1.7 metres tall and of medium to fat build.

He and the fourth culprit were both wearing light-coloured tops and dark trousers when last seen after the attack.

Chief Inspector Alice Lee Nga-lai, who is leading the investigation into the assault, said Mr Ho had not been able to provide a description of the attackers that was useful for the photofit process, but other witnesses of the attack in the McDonald's restaurant had helped.

The Democratic Party vice-chairman was bashed by three baton-wielding thugs in their 20s after he entered a McDonald's restaurant in Queen's Road Central.

He also received a threatening letter along with a cutter blade at his law firm on Thursday.

While police earlier had been unable to say if three or four attackers were involved in the beating, Chief Inspector Lee said they could now confirm that four men had carried out the attack.

The sketches will appear on Police Magazine on TVB Jade tonight.

Chief Inspector Lee said police were awaiting the results of tests of DNA samples and fingerprints taken from the restaurant.

She said police would also return to McDonald's tomorrow in a bid to jog the memories of witnesses and to find people who patronised the restaurant and area on Sundays, such as domestic helpers and shoppers.

Mr Ho will also go to the fast-food restaurant today to give a basket of fruit as a token of thanks to the staff.

Security was tightened around Mr Ho as he returned to work yesterday. His wife, Tang Suk-yee, drove him from his home in Tin Hau to Central under police and media escort.

His wife has kept a low profile since the attack as the couple fear the family could be the next target.

Mr Ho said he had had a good night's sleep, even though he had gone to bed late after receiving the death threat.

On his first day of work after the attack, Mr Ho remained in his office most of the time and only went out to have lunch with his university classmates at the Chinese General Chamber of Commerce.

'I have to work. I have to meet people. I have to maintain my community relationships. I have do things as usual. But certainly, my colleagues and I will be more cautious,' he said.

'I'm confident that we will be safe and we can work peacefully.'

Mr Ho said he had not asked for special police protection but would leave the matter to them.

Uniformed and plain clothes police officers were stationed around Mr Ho's home and office.

Meanwhile, both Democrat Lee Wing-tat and independent lawmaker Albert Chan Wai-yip have told police their street banners were recently vandalised.

Anyone with information about the four assailants is urged to contact police on 2860 7885.