6 June 2011 Last updated at
Yemen Crisis: Key players
The power struggle in Yemen took a new twist as President Ali Abdullah Saleh flew to Saudi Arabia for treatment after being wounded in a rocket attack on the presidential compound on Friday.
His vice-president is the acting head of state, but correspondents say the real jockeying for position involves Mr Saleh's sons and nephews and their rivals from the powerful Ahmar clan. Here's a look at some of the key players involved.
Now approaching his 70th year, President Ali Abdullah Saleh has a reputation as a tenacious political survivor. He has likened the task of ruling Yemen to "dancing on the heads of snakes".
President Saleh has placed sons and nephews in positions of military command
President Saleh's family hail from the Hashid tribal confederation, one of the two main tribal groupings in Yemen. They are among a minority of Yemenis practicing the Zaydi branch of Shia Islam, common in Yemen's northern highlands - the more settled regions of middle and southern Yemen follow the Shafi school of Sunni Islam.
received little formal education, joining North Yemen's military in 1958 and rising through the ranks. He was wounded several times during the civil war between Saudi-backed royalists and republicans before participating in a coup in 1974 and joining the military government that took over.
He became president of North Yemen in 1978 and took over leadership of the Republic of Yemen in 1990 following unification with the south.
Some of President Saleh's close family members accompanied him on the plane to Saudi Arabia in early June. But his son and nephews - who occupy key posts in the military - are reported to still be in the country.
President Saleh has several children. His eldest son, Ahmed Ali Abdullah Saleh, was widely suspected of being groomed to take over from his father before the popular uprising started. In an early bid to appease the protesters, President Saleh publicly guaranteed that he would not inherit the presidency.
Ahmed was born in 1970. After school in Yemen, he studied in the US and at Britain's elite military academy at Sandhurst. He was elected to parliament for Sanaa in 1997 and appointed as head of the Republican Guard in 2000. He was reported to have survived an attempt on his life in July 2002 and there were rumours of another assassination bid in 2004.
Ali Saleh al-Ahmar is another prominent figure. He is the president's half brother through the president's mother's second marriage. He served as head of the Republican Guard until he was replaced by Ahmed Ali Abdullah Saleh in 2000. He was later military attache in the Yemeni embassy in Washington, and director of the office of the head of the military.
Three nephews - Tariq, Yahya and Ammar - command security and intelligence units and have also been positioning themselves ahead of the expected transition. Yahya controls the central security services and anti-terrorism forces. Tariq is the commander of the special presidential guard and Ammar heads the national security forces.
Ammar and Yahya have co-operated with the US in fighting terrorism. Many Yemenis believe their presence in this transitional period is essential and welcomed by regional and international powers.
The historic rivalry between the Saleh and Ahmar families has been shifting to a second generation as key contenders try to position themselves for a transition. Recently, the Ahmar compound in the capital, Sanaa, has come under attack from government forces, while fighters loyal to the Ahmar clan have laid siege to ministries and other public buildings.
Shiekh Sadiq al-Ahmar (right) and brother Hamid are among a number of powerful siblings
The Ahmar family comes from the Amran governorate, just north of Sanaa and the heartland of the Hashid tribal federation. The family was headed by Abdullah bin Hussein al-Ahmar, founder of the Islamist Islah party, until his death in 2007.
Sheikh Sadiq al-Ahmar is now the overall leader of the tribal confederation. But he is seen as less powerful than his father, and is flanked by a number of prominent brothers.
The most high profile is Hamid al-Ahmar, a businessman and leading member of Islah, who is reported to have been plotting against President Saleh for years. He has repeatedly called for Mr Saleh's resignation.
Along with other businessmen he is believed to be providing financial backing for the demonstrators, and his Sabafon mobile mobile network has sent out text messages with the times and locations of protests.
Other brothers have recently stepped down from official positions as the political unrest in Yemen has escalated.
One, Sheikh Hussein bin Abdullah al-Ahmar, quit President Saleh's Governing People's Council on 28 February over the shootings of protesters.
Another, Himyar, was deputy speaker of parliament before he resigned in March.
Gen Ali Mohsen
A further figure expected to play a key role in the outcome of the unrest in Yemen is Gen Ali Mohsen al-Ahmar, who is related to the president through Ali Saleh al-Ahmar. He is a long-time ally of the Yemeni leader. Despite his name, he is not a member of the Ahmar family.
Gen Mohsen, a kinsman of President Saleh, announced his support for protesters in March
On 21 March, following the killing of dozens of unarmed protesters by Yemeni forces, he announced that he was backing the protest movement, but said his forces would continue to provide security and stability.
Over the years Gen Mohsen has played a leading role in trying to mediate Yemen's various internal conflicts.
He is the commanding officer of the 1st armoured tank division, which has sent units to a main square in the capital.
He also heads the north-west region, one of the country's four military sections.
The rivalry between him and the president's family has become known over the past few years. By 2008, there were rumours of a proxy war between Gen Mohsen's forces and those of Ahmed Ali Abdallah Saleh.
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