Zimbabwe's opposition MDC party is considering withdrawing from the 27 June presidential run-off vote, a party source has told the BBC. MDC leader Morgan Tsvangirai is said to be under pressure to pull out in view of reports of escalating violence against his supporters. At a summit in Brussels, the EU is threatening to impose fresh sanctions against Zimbabwe's authorities. President Robert Mugabe has blamed the opposition for the violence. Senior opposition MDC leaders are meeting in Harare to discuss whether or not to take part in the run-off vote. It is not clear if they will make a decision at the meeting. "There is a huge avalanche of calls and pressure from supporters across the country, especially in the rural areas, not to accept to be participants in this charade," opposition Movement for Democratic Change (MDC) spokesman Nelson Chamisa told Reuters news agency. If they do pull out, the MDC will be handing a victory to President Robert Mugabe, says the BBC's Caroline Hawley in Johannesburg, South Africa. Treason charge Meanwhile in Brussels, the EU has drafted a summit statement saying they are ready "to take additional measures against those responsible for violence". The EU document does not state what the additional measures might be. The EU already has an arms embargo against Zimbabwe and has placed travel bans on President Mugabe and other senior government and ruling party officials. The African Union and the Southern African Development Community are urged to deploy "a significant number of election monitors as soon as possible and to ensure their continued presence until the electoral process is completed and results officially declared," the statement says. Morgan Tsvangirai gained the most votes in the election's first round, but not enough to win outright. The opposition has suffered five violent deaths in recent days, among them the wife of Harare's mayor-elect. The MDC says at least 70 of its supporters have now been killed and 25,000 forced from their homes in a state-sponsored campaign of violence. One of its top leaders, Tendai Biti, has also been charged with treason and subversion. Source: BBC