HARARE (Reuters) - Zimbabwe’s main opposition said on Monday security forces were abducting its members in night raids to intimidate the party and stop it challenging President Emmerson Mnangagwa’s win in national elections.

Six people were killed in an army clampdown last week after violent protests and amid opposition claims of vote-rigging, in scenes reminiscent of the long rule of Robert Mugabe, when the security forces became a byword for heavy-handedness.

Opposition leader Nelson Chamisa has rejected Mnangagwa’s victory, which made him the first elected head of state since Mugabe’s removal from power in November, and has promised to use legal and constitutional means to challenge the poll outcome.

His spokesman Nkululeko Sibanda said lawyers would announce on Tuesday when Chamisa will launch a formal challenge to the election result in court.

Sibanda told Reuters that masked soldiers had abducted several MDC members in raids late at night and at dawn over the weekend in the capital Harare and assaulted people in townships, echoing Mugabe-era tactics against opponents.

He said soldiers had also visited the homes of opposition Movement for Democratic Change (MDC) chairman Morgen Komichi and party youth leader Happymore Chidziva, but the two were in hiding.

“The military is trying to discourage and to prevent anything and people from resisting the electoral theft by abducting and torturing people, but this will all come to nothing,” Sibanda said.

A girl looks on next to a defaced campaign poster of President Emmerson Mnangagwa in Harare, Zimbabwe, August 6, 2018. REUTERS/Philimon Bulawayo.

“We have these things, but people are not swayed.”

Amnesty International says more than 60 people were arbitrarily arrested in a “vicious campaign of torture, intimidation and suppression of dissenting voices.”

Chamisa is under pressure from angry supporters to indicate his next move after disputing the vote. The 40-year-old leader is faced with three choices, to accept defeat and move on, challenge the results in court or mobilize supporters for mass protests, which could lead to more bloodshed.

Army spokesman Overson Mugwisi did not respond to calls and questions send by Reuters. Police spokeswoman Charity Charamba said she was not aware of the abductions, adding “everyone has a right to report such incidences to the police.”

Anti-riot police and their water cannon left the MDC offices from where they were camped from last Wednesday.

Mnangagwa has said the army’s use of violence in Harare after the vote would be investigated independently, although he also suggested he understood the resort to military force, remarking that police were overwhelmed by opposition protesters.

On Monday, 27 MDC members were appearing in court to seek bail after they were arrested during last week’s violence.

“They simply want to instill fear into our people,” MDC secretary general Douglas Mwonzora said.

Zimbabweans had hoped the first post-Mugabe polls would move the country away from a history of disputed elections.

Mnangagwa faces the challenge of persuading the international community that the army crackdown and lapses in the election process will not derail his promise of political and economic reforms needed to fix a failing economy.