Image caption Businessman Neil Heywood died on 15 November in the Chinese city of Chongqing

A senior Chinese journalist has told the BBC that police knew UK man Neil Heywood had been murdered in Chongqing last November and that a cover-up began immediately.

Police panicked when they realised the case could be linked to top politician Bo Xilai and his wife, Gu Kailai.

It was only this month that authorities promised an investigation and named Ms Gu as a suspect.

Bo Xilai has been sacked, amid China's biggest political scandal in decades.

The 41-year-old British businessman was found dead in a hotel in Chongqing on 15 November. Local officials initially said he died of excessive drinking.

But police who arrived at the hotel immediately knew he had been killed, and panicked after they realised the case was linked to Mr Bo, the journalist told the BBC's Martin Patience in Chongqing.

Three of the investigators asked to resign, said Han Pingzao, a former correspondent for the People's Daily in the city.

Media playback is unsupported on your device Media caption Businessman Li Jun claims to have been tortured by police working under Bo Xilai

''They were terrified of the politician,'' Mr Han said.

'Torture claims'

It was at this point that former Chongqing police chief Wang Lijun became involved. In January, Mr Wang told his boss Mr Bo that he believed Ms Gu was involved in the murder.

''Bo Xilai was shocked when he heard the details,'' Mr Han said. ''He started sweating profusely.''

Separately, claims of torture have emerged against Bo Xilai and Wang Lijun.

Two men - one a businessman, Li Jun, the other lawyer Li Zhuang - told the BBC they had been victims and were innocent of the crimes they had been convicted of and now wanted justice.

Analysis Chongqing, the sprawling city of millions, was Bo Xilai's power base and some locals say that he ruled it like an "emperor". The apparent murder of Neil Heywood in the city last November triggered the country's biggest political crisis in years. The scandal led to the downfall of Mr Bo - who had been tipped to join China's top political body during the once-in-a-decade leadership change starting later this year. What had started in Chongqing suddenly became a national scandal - gripping the country. Many of the details remain shrouded in mystery and it is almost impossible to independently verify Han Pingzao's version of events - but it is an extraordinary insight into this scandal. The Chinese authorities have told the UK government that they will conduct a full and thorough investigation into Neil Heywood's death. But with so little transparency - and so much political intrigue - it is entirely possible that the full truth will never be known.

"They stabbed me with a pen if I disagreed with them. They slapped me, kicked me, hit me with an ashtray," a weeping Li Jun said.

Many Chongqing residents also told BBC correspondents of their support for the city's former party boss.

"Bo did great things for the people," one woman said.

The flamboyant Mr Bo - the nearest thing China has to a Western-style politician - made his name in Chongqing with two high-profile campaigns. One cracked down on organised crime, the other was to promote China's communist past.

Mr Wang, who has been closely identified with Mr Bo and his rise - he was tipped to be promoted to the party's top leadership before the scandal - was responsible for the anti-crime campaign.

After half an hour, Mr Bo approached Mr Wang and held both his hands tightly. Mr Wang thought he was safe then, the journalist said, but he was not.

He was sacked and subsequently sought refuge at the American consulate in Chengdu, where he reportedly told US officials about the murder and attempted to defect.

Mr Wang was eventually persuaded to leave the consulate, emerging into the waiting arms of the police and an investigation.

'Extraordinary scenes'

The events surrounding Mr Bo and his wife have become the biggest political scandal in China in years, ahead of a leadership change in Beijing due to get under way in October.

There were ''extraordinary scenes'' on the day that Mr Bo's sacking as Chongqing party chief was announced last month, Mr Han said.

''Chongqing party officials attended sessions at various departments to hear how the central government had decided to handle the case,'' he added.

This came right after China's annual parliamentary meeting in Beijing. In a news conference at the end of the parliamentary session, Premier Wen Jiabao took - and answered - a direct question on the Wang Lijun incident.

TIMELINE: BO XILAI SCANDAL 2 Feb: Chongqing police chief Wang Lijun is demoted, confirming he has fallen out with the city's Communist Party boss, Bo Xilai.

Chongqing police chief Wang Lijun is demoted, confirming he has fallen out with the city's Communist Party boss, Bo Xilai. 6 Feb: Mr Wang flees to the US consulate in nearby Chengdu, where he spends the night. Many believe he went there to seek asylum.

Mr Wang flees to the US consulate in nearby Chengdu, where he spends the night. Many believe he went there to seek asylum. 5 Mar: China announces that Bo Xilai has been removed from his post in Chongqing.

China announces that Bo Xilai has been removed from his post in Chongqing. 20 Mar: Rumours suggest that Mr Bo could be linked to the death of British businessman Neil Heywood, who died in Chongqing last November.

Rumours suggest that Mr Bo could be linked to the death of British businessman Neil Heywood, who died in Chongqing last November. 26 Mar: UK government confirms it has asked China to re-examine Mr Heywood's death.

UK government confirms it has asked China to re-examine Mr Heywood's death. 10 Apr: China says Bo Xilai has been suspended from party posts and his wife is being investigated over My Heywood's death.

"The present Chongqing municipal party committee and the municipal government must reflect seriously and learn from the Wang Lijun incident," he said.

While Mr Bo's name was not mentioned, the comment was understood to be a public criticism directed at him.

''There were thousands of officials going in and out all day,'' said Mr Han. ''On the same day, late in the evening, the news was broadcast to the whole country.''

A few weeks later state media reported that Ms Gu and Zhang Xiaojun, an orderly at Mr Bo's home, had been arrested. Mr Bo is also under investigation for ''serious discipline violations''.

The Chinese authorities have promised the UK government a thorough investigation into Mr Heywood's death.