Election officials in Liberia reported low voter turnout on Tuesday in the country's disputed constitutional referendum.

Liberians decided on four proposed amendments to the constitution. The most controversial change would reduce the number of consecutive years a presidential candidate must have resided in Liberia, from 10 to five.

Other proposed changes would delay the presidential and parliamentary elections from October to November and eliminate run-off votes in legislative polls.

Liberian's main opposition party called for a boycott of the vote, saying the proposed changes would make it easier for President Ellen Johnson Sirleaf to retain power. Some also complained that the referendum was being held too close to election season.

As voting began, Liberia's National Election Commission acknowledged a printing error on one question of the ballot. Voters were supposed to choose whether to increase the retirement age for Supreme Court judges from 70 to 75, but the ballot listed 75 as the only option. Officials say voters were instructed how to vote, despite the error.

Official election results have not been released. Two-thirds of voters must approve the changes for them to be adopted.

Liberia is still recovering from 14 years of civil unrest and war that ended in 2003. President Ellen Johnson Sirleaf was elected president in the country's first post-war polls in 2005.