The latest flashpoint is around the town of Chinhoyi, 75 miles from Harare.
Mr Mugabe has stepped up his diatribe against Britain, and it seems clear the England team could become a target for pro-government demonstrators.
A Cricket Board spokesman said: "We are continuing making plans to go ahead but we are in contact with the Foreign Office. If it deteriorates very badly we will need to take their advice as to whether to go ahead."
The Foreign Office said: "The decision is theirs. We will give our assessment of the situation on the ground and the likelihood of difficulties. We are very concerned about what is happening so we are monitoring the situation very closely."
Sources close to the Cricket Board, however, said there was a growing momentum against the tour.
While ministers in London have condemned the Zimbabwe government for its handling of the farm protests, they have steered clear of calling for a sporting boycott of the country.
But some Labour MPs believe Britain should go further. Gareth Thomas, secretary of the all-party parliamentary sports group, called for the tour to be cancelled.
Tory shadow foreign secretary Francis Maude said Mr Mugabe should be banned from the Commonwealth meeting of government leaders in Brisbane in October.