Speaking on an RTHK radio programme on Saturday, Lam said she hoped Chan’s decision would help calm social sentiments in Hong Kong, now in its fifth month of anti-government unrest sparked by opposition to an extradition bill which the government linked with Chan’s case.

“It’s an ending that brings relief,” she said. “For the social unrest, I hope that this will bring about a relaxing feeling to society,” she said.

“The victim’s parents have been writing to me, asking the government to find ways to bring justice … I hope they can be relieved now.”

Chan’s surprising decision to turn himself in came just ahead of his release after 18 months behind bars.

He is wanted in Taiwan for allegedly killing his pregnant ­girlfriend, Poon Hiu-wing, in Taipei in February last year.

Soon after her death, Chan returned to Hong Kong and was arrested for money laundering over the use of the woman’s cash and property, but could not be handed over to Taiwan authorities without an ­extradition deal between the two jurisdictions.

The government claimed, when introducing the hugely controversial extradition bill, that sending Chan to Taiwan was a key motivation.

Taiwan’s Mainland Affairs Council on Saturday blamed Hong Kong authorities for, as it saw it, trying to evade their responsibility to bring Chan to justice. Insisting that it had done its part to investigate the case, it said Hong Kong authorities had ignored its requests for help.

Taipei’s Ministry of Justice said it had not been given any evidence by Hong Kong related to the case. It requested Hong Kong continue detaining Chan after he was released from prison to protect the integrity of any evidence.

Lam said Hong Kong had no legal grounds to detain Chan over the killing, which took place in Taiwan.

Taiwan urges Hong Kong to pursue murder suspect who sparked extradition crisis

“We have received a letter faxed to us by Hong Kong police, saying Chan Tong-kai is willing to come to Taiwan to surrender to police,” the Criminal Investigation Department was quoted as saying by the semi-official Central News Agency. “The Hong Kong side said it would provide legal aid for the arrangement of him to come to Taiwan, but because there is no such precedence before, the department will discuss with relevant agencies on how the arrangement should be made.”

Chan’s decision was first confirmed on Friday by Reverend Canon Peter Koon Ho-ming, a top Anglican priest who has been visiting Chan weekly in jail.

Lam said the government had not asked anyone to get in touch with the suspect, but added: “I know that Koon cares a lot about young inmates, and he has been updating me on his meetings with Chan.”

The city leader was asked whether the extradition bill – which sparked the city’s biggest political crisis in decades – had been unnecessary, when the case could have been resolved by having Chan turn himself in.

But she said Chan’s case was not the only reason the government pushed the bill, which would have allowed the transfer of fugitives to jurisdictions which lack an extradition agreement with Hong Kong, including mainland China and Taiwan.

“We wanted to handle a problem which had existed in our legal system for a long time. There is no mutual legal assistance with Taiwan, and the Hong Kong police cannot use the city’s law to prosecute someone who has committed a murder or another crime in Taiwan,” she said.

As Chan is a wanted man in Taiwan, he is likely to be taken into custody upon his return to the self-ruled island. But questions remained as to whether he would face capital punishment, which is still in place there.

After a Commercial Radio programme, Lam did not answer when asked if she would write to Taiwanese authorities asking that he not be sentenced to death.

Criminal lawyers in Taiwan have said prosecutors cannot seek plea bargains for serious crimes such as murder, and the death penalty remained a possibility for a murder conviction.

But Joseph Lin, a veteran criminal lawyer in Taiwan and chairman of the Judicial Reform Foundation, said Chan, if found guilty, would probably not be executed.

“Especially with calls to abolish capital punishment in Taiwan, most judges would find reasons not to give death sentences,” Lin said, adding that other options included a jail sentence of more than 10 years, up to life imprisonment.

If Chan had surrendered himself before the case was known to law enforcement or had been widely reported in the media, Lin said, the death penalty would not be on the cards as a reduced sentence is guaranteed.

Should he turn himself in, such a reduction is not guaranteed but judges may still consider it, Lin added.