Vitaly Shishov, the head of the Kiev-based Belarusian House in Ukraine (BDU) organization, was reported missing by his partner on Monday after going for a run, police said. By Tuesday morning, the activist was found hanged in a forested area of a park near his Kiev home.

Ukrainian police opened a criminal case and said they would investigate whether Shishov's death was a suicide or "premeditative murder meant to look like suicide."

The BDU helps fleeing and exiled Belarusians find accommodation, jobs and legal advice in Ukraine. In a statement on Tuesday, the BDU said Shishov had been "under surveillance" and that they had received warnings about possible threats prior to his death.

Belarus has been in political and social turmoil since last year, when a disputed election led to mass protests, then a violent crackdown by President Alexander Lukashenko that was condemned by the international community and sparked an exodus of dissidents from the country.

In a news conference on Tuesday afternoon, head of Ukrainian national police Ihor Klymenko said that Shishov's body had been found with "abrasions" and "peeled skin" in several places, wounds that "can be characteristic of a onetime fall." Klymenko did not elaborate on the fall he referred to.

The site where Shishov was found dead in Kiev.

Security cameras recorded Shishov leaving his house around 9 a.m. local time Monday, and he was supposed to be back at 10 a.m., the BDU said in a statement Monday.

Shishov "went out, presumably for a daily jog (his sports things were not found at home) and did not return. Several so-called 'jammers' were made from his number, but now it is impossible to contact him."

The BDU added that Shishov's phone was disconnected from location tracking, and he did not have his watch or fitness bracelet on. The team called the police, which searched the woods with tracker dogs.

Police said they would question witnesses and analyze footage from security cameras, and asked those who knew Shishov to come forward with any relevant information on the last few weeks of his life and possible threats he faced.

Shishov's friend and colleague Yury Shchuchko told Current Time TV that he had learned of the activist's disappearance through his girlfriend, and that a group of them saw the body after going out and searching for him.

"At 6 a.m. we went out to search. The police at that time started canvassing the surrounding buildings. We went to the park and found what we found," he told Current Time TV, adding that there were "traces of violent death" on Shishov's face.

On Tuesday the BDU said Shishov was "under surveillance" before his death and described him as a threat to the Lukashenko regime.

"Vitaly was under surveillance. There were appropriate notifications to the police about the facts. Also we were repeatedly warned by local sources and by our own people in Belarus about all kinds of provocations up to kidnapping and liquidation," BDU said in a Tuesday statement. "Vitaly treated these warnings with stoicism and humor, stating that at least in this way, it would be possible for BDU to get out of the info vacuum."

Shchuchko said he'd received a worrying phone call from Shishov the week prior to his death. "Vitaly called me last week and asked me to take care of his loved ones because he had some strange feeling. I didn't hear any more details," he told Current Time TV.

On Tuesday, Belarusian opposition leader Svetlana Tikhanovskaya said it could have been a crime but that she would withhold judgment until the findings of the police probe were in.

"I prefer to wait for the results of investigation ... because I understand the background of this death. I would say it is a crime but I can't say it without results of an investigation," Tikhanovskaya said outside Downing Street in London following a meeting with UK Prime Minister Boris Johnson.

Ukraine's Foreign Minister Dmytro Kuleba expressed shock over the "tragic news" of Shishov's death on Twitter, saying "Ukraine will do everything possible to fully investigate the case: it is of utmost importance for us to reveal the truth about his tragic death."

A safe haven

Shishov's death comes as Belarus faces increasing international scrutiny after a Belarusian Olympic sprinter alleged that she was forcibly removed from the Tokyo Games and told to return home against her will, where she fears arrest.

Ukraine, Poland and Lithuania have become safe havens for Belarusians since the unrest began last year.

Hundreds of thousands of Belarusians attended mass protests across the country after Lukashenko declared victory in the August vote, in some of the biggest demonstrations in the country's recent history.

Thousands of people were arrested in the protests, which were brutally suppressed by authorities amid widespread reports of abuse and torture.

Police bodycam and dashcam footage, provided by defectors from the police force, have shown the extraordinary ferocity of riot police against protesters who are unarmed and peaceful, many of them teenagers.

Many have since fled the repression of Lukashenko's regime, sometimes swimming through rivers and crawling through sludge to illegally cross the border into Ukraine.

Kristina Timanovskaya, the Belarusian Olympic sprinter, said representatives of the Belarus national team tried to forcibly send her back to her home country after she criticized national sporting authorities for entering her into the 4x400 meter relay in Tokyo without her consent.

Timanovskaya did not say exactly what she feared she would be jailed over, but Belarusian athletes have faced retaliation, been detained, and excluded from national teams for criticizing the government after last year's protests.

She has since received a humanitarian visa from Poland, and will travel there in the coming days, according to Polish authorities. On Tuesday, the International Olympic Committee said it will launch a formal investigation into Timanovskaya's situation.