Sanaa:
Yemeni Shiite rebels were said to be close to agreeing Friday to sign a deal to end deadly fighting north of the capital with Sunni fighters of the Islamist Al-Islah party.
Here is a backgrounder on political-military groups in Yemen:- Ansarullah
Also known as Zaidis and Huthis after their leader Abdelmalek Badreddin al-Huthi, the Shiite rebels have been at war with the government since 2004.
They are concentrated in the rugged northwestern mountains where the Shiites are a majority in otherwise Sunni-majority Yemen.
The Huthis have complained of marginalisation since the rule of now-toppled autocratic president Ali Abdullah Saleh.
Ansarullah demands the resignation of the government, a say over the appointment of ministers and access to the sea.
Initially its rebellion sought to defend Zaidism, a branch of Shiite Islam, because of an increased Sunni presence in northwest Yemen.
Saada, the Huthi stronghold, is the birthplace of Zaidism, founded in 898 by the creation of a politico-religious regime dubbed the Zaidi Imamate toppled in 1962 by a military coup that established the republic.
- Al-Islah
The Sunni Islamist Al-Islah (Reform) party was one of the pillars of power under former president Ali Abdullah Saleh.
However, in August 2011 it switched to the opposition, forming a coalition with six other parties in a united front against Saleh who bowed out in January 2012.
The conservative Al-Islah draws its support and membership mainly from heavily armed Sunni tribesmen, and it is highly influential within the country's armed forces.
In recent fighting with the Huthi rebels north of the capital Sanaa, Al-Islah fighters were supported by the army.
- Al-Qaeda
Al-Qaeda in the Arabian Peninsula was formed in January 2009 as a merger of the Yemeni and Saudi branches of Al-Qaeda, and is seen by Washington as the most active branch of the jihadist network.
It took advantage of the weakness of the central government during the anti-Saleh uprising in 2011 to seize large swathes of territory across the south and southeast.
Also active in central Yemen and east of Sanaa, AQAP has launched many deadly attacks on the armed forces and symbols of central authority, including in the capital itself.
Al-Qaeda's first known attack in Yemen dates back to 1992, when bombers hit a hotel that formerly housed US Marines in the southern city of Aden, killing two non-American citizens.
In 2000, an Al-Qaeda suicide attack on the naval destroyer USS Cole in Aden killed 17 US military personnel.
AQAP is led by Nasser al-Wuhayshi, a Yemeni who tunnelled his way out of prison in 2006 along with 22 other militants. His deputy is a Saudi, Said al-Shihri, who was freed from Guantanamo Bay by the United States in 2007.
- The Southern Movement
The Southern Movement is an umbrella group in the region that belonged to former South Yemen, which was an independent state until 1990.
It brings together groups with diverse demands ranging from social and economic equality with the north to complete secession.
Some members of the Southern Movement advocate armed force to achieve their aims, but their operations have been limited in scope.
The government's plans for a six-region federation in Yemen to address the grievances of the regions have been rejected by both the Shiite rebels and southern separatists.