Eight Liberian opposition parties say they are pulling out of the country's recent presidential election, claiming the vote counting process is fraudulent and undemocratic.

In a statement Saturday, the parties said election officials have manipulated the results in favor of incumbent President Ellen Johnson Sirleaf, who is leading in the latest results released Friday.

Those pulling out include Ms. Sirleaf's top rival Winston Tubman, who is in second place, and the third-place challenger, former rebel leader Prince Johnson.

Liberia's Election Commission has not responded directly to claims of fraud. It is calling on all parties to address complaints through proper legal channels.

Election officials said Friday that Ms. Sirleaf was ahead with more than 45 percent of the vote. Tubman had less than 30 percent, and Johnson about 11 percent.

Election observers from the Economic Community of West African States have said the October 11 vote was largely free and fair, and that ballot counting is proceeding smoothly. The U.S.-based Carter Center noted only minor irregularities.

In related news, Liberian police say an office occupied by the country's ruling party was set on fire Saturday in the capital, Monrovia. No injuries were reported, and police are investigating the incident.

Liberia's electoral commission has until October 26 to announce final results.

The vote was Liberia's second national election since the end of a 14-year civil war in 2003.