The US state of Maryland has voted in favour of civil equal marriage in a public referendum.

According to Politico, with more than 80% of precincts declared, the measure has been supported by 57.8% against 42.2%.

In the run up to the vote Hollywood actor Brad Pitt agreed to donate $100,000 (£62,000) to help the Human Rights Campaign raise money for its efforts to support equal marriage initiatives in several US states, including Maryland.

New York Mayor Michael Bloomberg, who previously studied in the state, also donated $250,000 (£155,000) to the pro-marriage equality campaign in Maryland last week.

A bill to legalise same-sex marriage in Maryland was passed by the state General Assembly in February 2012 and signed into law on 1 March 2012, by Governor Martin O’Malley.

However, opponents of marriage equality successfully gathered enough signatures to force a referendum on the decision.

Maryland’s equal marriage law will come into force on Thursday 6 December 2012.

Results from equal marriage referendums in Washington state and Minnesota are due later on Wednesday.

In Maine, residents have voted to support marriage equality in a landmark state ballot there.