HARARE, July 11 (Xinhua) -- Zimbabwe's opposition MDC Alliance on Wednesday staged another demonstration in the capital Harare to demand key electoral reforms ahead of the July 30 vote.

The demonstration by thousands of party supporters is the second in six weeks as the party piles pressure on the Zimbabwe Electoral Commission (ZEC) to accede to its demands to have access to what it describes as a credible voters' roll and printing of ballots.

Addressing supporters at the Africa Unity Square before they marched to ZEC offices in downtown Harare to present a petition, party president Nelson Chamisa said the party will be forced to stage sit-ins at ZEC if it refuses to listen to it.

ZEC has denied claims by the opposition party that the voters' roll it released is not credible and insists that it will not avail pictures of the voters as is being demanded by the MDC Alliance in order to protect voters' privacy.

ZEC has also said it is not obliged by law to grant political parties access to the printing of the ballots.

Senior leaders of the party submitted a petition to ZEC demanding a raft of electoral reforms which they said if not availed "will threaten the holding of the election scheduled on the 30th of July 2018."

Among others, the MDC Alliance is demanding the urgent release of a complete biometric voters' roll in searchable and analyzable form with requisite biometric features, an independent audit of the voters' roll and the immediate cessation of the printing of the ballot paper pending agreement on observation by stakeholders.

The party is also demanding an independent investigation into the matter in which the ruling ZANU-PF allegedly accessed voter information that was supposed to be in the sole custody of ZEC.

ZANU-PF this week allegedly sent personalized messages to some registered voters soliciting their votes.

In his address after the march, the 40-year-old Chamisa accused President Emmerson Mnangagwa's ZANU-PF of working with Russians to tamper with the ballots.

"We are not going to allow foreigners to interfere with our own electoral process. We are going to take up that matter and we will not budge," he said.

He reiterated that there will be no elections on July 30 if they do not agree with ZEC on the issue of the voters' roll and ballots.

The opposition leader, who is Mnangagwa's main challenger, has indicated that his party will not boycott the election.

He said the party would intensify demonstrations in the coming weeks if ZEC does not accede to its demands.

"This is the last demonstration that we are going back home. In the next demonstration we will not go back home. Next week is going to be decisive on the way forward. We are going to engage ZEC about the ballot issue and if not addressed we will go into red gear," Chamisa said.

Mnangagwa, who took over from former president Robert Mugabe in November last year, has promised to hold free and fair elections.

His government has invited Western observers to observe the polls.

Mnangagwa battle it out with 22 other presidential candidates.