The poorest Arab nation faces economic hardships aggravated by a southern separatist movement, a growing threat from al Qaeda militancy and a long-running but intermittent conflict in the north.
Thousands uprooted
High malnutrition rates
Guns everywhere
Aid agencies say the northern conflict has left tens of thousands homeless in a remote mountainous area in Saada province, near Saudi Arabia, to which outside access is restricted.
The conflict between Abdul-Malik al-Houthi's Shi'ite rebels and the government has raged on and off since 2004 despite ceasefires and pledges of reconstruction.
Thousands of people have fled their homes, including families from Yemen's tiny but ancient Arabic-speaking Jewish community, and towns have come under siege.
The fighting escalated in August 2009, raising the total number of displaced to some 150,000 -
most of them in Saada province. Journalists and diplomats are barred from the rugged mountain area and the few aid agencies operating there are constrained by security concerns.
Many of the displaced have moved into camps. In an arid, drought-prone region, providing water is one of the main tasks for aid agencies.
An unknown - and probably far greater - number of people have sought refuge with friends, relatives or other households in nearby cities or moved away from the region completely. Some of them have had to pay smugglers to get them out.
The rebels are adherents of the Zaydi branch of Shi'ite Islam and a strongly tribal minority in mostly Sunni Muslim Yemen. They oppose Yemen's close ties with the United States and say they are defending their villages against government oppression.
The rare murder in July 2009 of three foreign aid workers kidnapped in Saada province gave the government a jolt over an apparent resurgence of al Qaeda in the same northern area.
The Houthi rebels have no known links to al Qaeda, which follows a strict brand of Sunni Islam. And tribesman, disgruntled over marginalisation, have often abducted foreigners - usually tourists - but have rarely killed them.
But the insurrection in the north has underlined Western and Saudi fears that instability may spiral out of control and allow al Qaeda militants to entrench themselves in the ancestral home of the network's leader, Osama bin Laden.
Sunni Muslims dominate the government and make up most of Yemen's 19 million people. The Zaydis, the closest Shi'ite sect to mainstream Sunni Islam, make up most of the rest.
Yemen is awash with weapons, with some reports saying there are 40-50 million guns in the country.
Aid agencies say malnutrition rates are high among displaced families and could go higher without adequate food aid. The World Food Programme had to cut monthly rations when it ran short of money in mid-2009. The fighting has led to food scarcity in markets and hit farm output in a country with rapid population growth.
North Yemen reunited in 1990 with the weaker Marxist south, where a secessionist movement has also caused instability since 2007.
Some in the south say the north has discriminated against them and exploited their region's resources.
The country's economy is heavily dependent on dwindling oil supplies. It has high levels of unemployment, rapid population growth and diminishing water resources.
Yemen, one of the poorest countries outside Africa, also hosts 140,000 refugees from countries like Somalia and Eritrea across the Gulf of Aden, according to the U.N. High Commissioner for Refugees.
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Girls attend class in a school at al-Mazraq camp in the western Yemeni province of Hajjah November 25, 2009. The camp, which is Yemen's main camp for people fleeing fighting between ...