President Ali Abdullah Saleh of Yemen has agreed to step down under a 30-day transition plan aimed at ending violent unrest over his 32-year rule, the BBC reported.

Officials in the capital Sanaa confirmed the government had accepted the plan drawn up by Gulf Arab states.

Saleh will hand power to his vice-president one month after an agreement is signed with the opposition, in return for immunity from prosecution.

At least 120 people have died during two months of protests.

The US has welcomed the announcement; a statement from the White House urged all parties to "swiftly" implement a peaceful transfer of power.

Opposition leader Yassin Noman was quoted by Reuters news agency as saying he welcomed news of the handover but would not take part in a proposed national unity government.

The opposition have been insisting they will not accept immunity from prosecution for Saleh and his family.

If Saleh steps down as expected, he will join Tunisia's Zine al-Abidine Ben Ali and Egypt's Hosni Mubarak as the latest Arab leader to lose power because of a popular revolt this year.

Tariq Shami, a spokesman for Yemen's ruling party, told Reuters the party had informed the Gulf Cooperation Council "of their acceptance of the Gulf initiative in full".

Hundreds of thousands of people attended a rally in support of Saleh in Sanaa on Friday but comparable numbers turned out for demonstrations against him in both the capital and the southern city of Taiz.

On Saturday, a general strike called by the opposition caused disruption in Taiz, the port city of Aden and other towns, although apparently it had little effect in the capital.

Yemen is the Arab world's most impoverished nation and, even before the current protests, it was becoming increasingly chaotic, with both al-Qaeda and separatist challenges to the government's authority.

Saleh suffered a major political reversal last month when a slew of ministers and ambassadors resigned in protest at the shooting of 45 people at a demonstration in Sanaa.

The president promised earlier not to renew his presidency in 2013 or hand over to his son. He has made - and broken - similar promises in the past.

Members of the opposition coalition say they are wary of loopholes that could keep Saleh, a canny politician, in office.

One opposition leader told Reuters that ending the protests would be a major sticking point.

The opposition, the unnamed leader added, did not fully control the hundreds of thousands of people, many of them youth activists, who have taken to the streets.