An official source at the presidential office described the opposition’s offer as “contradictory, violating the constitution and sets that stage for chaos.”

“The constitution is the reference to the rulers and the people and any attempt to violate the constitution is unacceptable since it implies serious risk, threatening the nation's security and stability,” the source was quoted by Saba News Agency, adding, “the peaceful and smooth transition of power can't be carried out through chaos, but through resorting to the will of the people which was expressed through the ballots boxes.”

On Thursday, opposition offered Saleh a road map for a smooth transfer of power by the end of the year.

The opposition offer includes the trial of police and members of the security forces who were responsible for the deaths and injuries of protesters, as well as compensation for those wounded and the families of those killed.

The opposition on Friday said Saleh was sticking to an earlier plan to step down in 2013 but had agreed to a proposal by religious leaders to revamp elections, parliament and the judicial system.

Saleh, an ally of the United States in its battle against an Al-Qaeda wing based in his country, has struggled to cement a truce with rebels in the north and quell a budding secessionist rebellion in the south.

Protests have taken place across Yemen, a country of 23 million.

The protesters say they are frustrated with widespread corruption and soaring unemployment in a country where 40 percent of its 23 million people live on $2 a day or less and a third face chronic hunger.

Separately Yemen's Deputy Minister for Youth and Sports, Hashid Abdullah Al-Ahmar, resigned from the ruling party on Saturday in protest at the use of violence against anti-government demonstrations, a source close to him told Reuters.

His resignation comes just a day after an influential ally of the president, Ali Ahmad Al-Omrani, a tribal leader from the southern Al-Baida province, resigned.

Omrani's resignation came a week after nine Parliament members from the General People's Congress Party (GPC) resigned.

Earlier on Saturday witnesses told Reuters three protesters were wounded on Friday evening when Yemeni security forces fired into the air and used tear gas to disperse demonstrators at a sit-in in the southern port city of Aden.

Protesters were dispersed after they had gathered at a square in the city's Sheikh Othman district following Friday prayers, the witnesses said.

Possibly more than 100,000 protested on Friday in one of the largest demonstrations in Sanaa yet and similar numbers rallied in Taiz, south of the capital, a Reuters reporter said.

More than 20,000 protesters marched in Aden and tens of thousands marched in Ibb, south of Sanaa.

Rebels in the north of the country on Friday accused the Yemeni Army of firing rockets on a protest in Harf Sufyan, where thousands had gathered. Two people were killed and 13 injured.