Image copyright Getty Images Image caption Russian stock markets and the rouble fell further on Monday on the back of a fresh slump in oil prices

Oil prices have fallen to their lowest level since 2003, sinking below $28 a barrel before recovering slightly on Monday.

Analysts say the drop has been driven by oversupply, coupled with a fall in demand because of a slowdown in economic growth in China and Europe.

There are fears that the lifting of Western sanctions on Iran could worsen the existing problem, as the country prepares to pump more oil into the market.

The effects of falling prices are being felt by economies around the world.

But oil producing nations that rely on exports have been particularly hard hit, with many now feeling the social and, in some cases, political impact.

Russia

As one of the world's largest oil producers, Russia has been a prominent victim of the plunging prices.

About half of Russia's budget revenues currently come from energy exports.

The rouble is also under pressure from economic sanctions that the West imposed on Russia for its involvement in the Ukraine conflict.

On Monday, the national currency dropped to new lows, with the exchange rate dipping to 79 roubles to the dollar and 86 roubles to the euro - something not seen since December 2014.

Government departments have been ordered to cut spending by 10%, repeating a policy imposed in 2015, Reuters reported.

Russian Prime Minister Dmitry Medvedev has warned that the country's 2016 budget may have to be revised as a result of the "unpredictable" oil prices.

President Vladimir Putin's approval ratings remain sky high, at around 85%, but ordinary people are increasingly struggling with rising food prices.

Analysts say keeping the lid on any discontent will be a top priority for the Kremlin as the economic woes look set to worsen.

Saudi Arabia

Saudi Arabia's income from oil fell by 23% last year, highly significant in an economy where around 73% of total revenues comes from the industry.

The country announced a budget deficit nearing $100bn (£68bn).

After the lifting of sanctions on Iran, share prices in oil-rich Gulf states dropped sharply - with the Saudi Arabia Stock Exchange falling 5.4% on Sunday.

With no prospect of higher oil prices soon, experts say the kingdom's conservative rulers are poised to introduce reforms. as they attempt to avoid political discontent.

In December, King Salman raised the price of subsidised, cheap petrol by 40%. There are also plans to decrease other subsidies, reduce the growth of public sector salaries and limit the country's dependence on oil.

With Saudi Arabia's regional rival, Iran, entering the international market, experts say the kingdom is unlikely to back any efforts by the Organization of the Petroleum Exporting Countries (Opec) to reduce production and increase oil prices.

Azerbaijan

President Ilham Aliyev has ordered his government to draw up a series of special measures to revitalise his country's economy in the face of tumbling oil prices.

The plans would include a major programme of privatisation and strengthen regulations on the currency market, his office said in a statement (in Azeri).

The announcement comes after dozens of people were arrested during protests over rising food prices and worsening economic conditions in the city of Siyazan last week.

Image copyright Meydan TV Image caption Footage of the protests was shown by independent station Meydan TV

Azerbaijan's economy is heavily dependent on oil exports. Nearly half its GDP in 2014 came from the oil sector.

The country's currency, the manat, has fallen dramatically in value.

Analysts say Azerbaijan's government has done little to improve other industries, despite repeated warnings about the dangers of relying on oil.

With the volatile currency, and the range of people suffering increasing, protests may become more common.

Venezuela

Venezuela has the world's biggest known oil reserves, and oil exports account for as much as 95% of the country's revenues.

However, the huge fall in oil prices in the past 18 months has slashed revenues by 60%.

On Saturday, Venezuela's government announced a 60-day economic emergency to deal with a worsening economic crisis. The edict includes tax increases and puts emergency measures in place to pay for welfare services and food imports.

Image copyright Reuters Image caption People are forced to line up to try to buy meat in Caracas as Venezuela's government declares an "economic emergency"

The government's move came as official figures showed that the Venezuelan economy had contracted by 4.5% in the first nine months of 2015.

Meanwhile people in Venezuela have been suffering from food and basic goods shortages.

Experts say this led many to vote for the opposition coalition, which won an overwhelming victory in December's legislative election and dealt a huge blow to the country's Socialist movement.

Nigeria

Nigeria is Africa's biggest oil producer but lacks sufficient refining capacity and has to import most of its fuel.

President Muhammadu Buhari has already said falling oil prices are having "a painful effect" on the country's economy.

Despite this, he announced plans in December to raise government spending in 2016 by 20%, by seeking overseas funding.

However, reports suggest the president requested the withdrawal of the 2016 budget on Sunday, in order to make changes.

As well as falling prices, the industry is also dogged by violence in the country and oil spills.

On Monday, Nigeria's state oil company shut down crude oil flows to two of its four refineries after weekend attacks on pipelines, a company spokesman told Reuters news agency.

The closures at the Kaduna and Warr installations come amid efforts to boost refining and wean the country off imports.