Commentators suggest it is the latest in the series of attempts by Robert
Mugabe's Zanu PF to force Mr Tsvangirai to pull out of the fragile
coalition, formed in 2009 after disputed elections the previous year.
More than 100 MDC activists and politicians have been arrested in the past
month, and an attempt at a North African-style protest was met with a
massive police presence.
Were Mr Tsvangirai to quit, Zanu PF could be left in complete control of the
country once again and would have the right to call elections unilaterally.
The failing health of Mr Mugabe is thought to be a factor in Zanu PF's desire
for early elections.
Last week, Mr Tsvangirai said he wanted a "divorce" from Mr Mugabe
after Elton Mangoma, the MDC-supporting Energy and Power Minister, was
arrested.
Mr Mangoma, who was released on bail on Tuesday after five days in custody,
has been charged with criminal abuse of office over an allegedly fraudulent
fuel deal.
Government sources say the arrest was "politically motivated" and a
local newspaper report claimed on Tuesday that Mr Mangoma had vetoed a fuel
deal from which Zanu PF would have profited.
An MDC spokesman named those arrested in Sunday's police raid on its Harare
headquarters Harvest House as Desmond Ncube, the MDC Youth Assembly National
Coordinator, and two security staff, Trust Phiri and Hebert Murori.
"They remain in custody though no charge has been levelled against them,"
the spokesman added.
A report in the Zanu PF-supporting Herald newspaper suggested the raid was in
response to an attack on a Zanu-PF district chairman, who was allegedly
struck over the head with an iron bar by men wearing MDC baseball caps.
Lashias Ncube, a Zimbabwean
political commentator and managing director of a media firm in South Africa,
said it was clear police were acting partially.
"It's fairly obvious that the regime is trying to do whatever it can to
demoralise the opposition and beat them into submission," he said.
