A Zimbabwean rights group says police have arrested 13 of its members who accused authorities of harassing opponents of President Robert Mugabe.

Stendrick Zvorwadza with Restoration of Human Rights says the members were detained while protesting outside a court in the capital, Harare, on Wednesday.

The protesters had gathered at the site to press for the release of seven members of Prime Minister Morgan Tsvangirai's MDC party.

The MDC is in a tense power-sharing government with President Mugabe's ZANU-PF party.

Police jailed the MDC members in May, accusing them of being involved in the death of a police officer. The suspects have not been formally charge but have denied the allegation.

Zvorwadza says the rights group had gathered to demand that the courts and police stop targeting Mugabe opponents.

Earlier this month, police briefly detained two MDC cabinet ministers and about 20 other party officials. It was the largest single arrest of ZANU-PF opponents since Zimbabwe's unity government came to power.

Mr. Mugabe was forced into a power-sharing government after a disputed and violence-plagued election in 2008.

Since then, the MDC has accused police loyal to President Mugabe's political party of harassing its leaders and blocking the party from holding rallies.