* Dollar, treasuries jump after North Korea shells South
* Irish debt crisis puts euro under heavy pressure <EUR=>
* U.S., European, Asian stocks fall
* Book-squaring before U.S. Thanksgiving accelerates decline
* Coming Up: API oil inventory data; 2130 GMT (Adds detail, comment, updates prices)
By Christopher Johnson
LONDON, Nov 23 (Reuters) - Oil fell below $81 on Tuesday as the dollar gained after an exchange of artillery fire between North and South Korea and as the euro fell on fears Ireland's debt crisis might lead to problems elsewhere in Europe.
North Korea fired dozens of artillery shells at a South Korean island on Tuesday, killing two soldiers and prompting return fire, in one of the heaviest attacks on the South since the Korean War cease-fire in 1953. [
]European and Asian stock markets as well as U.S. stock futures fell while 10-year Treasury futures <TYc1> rose as tensions between the two Koreas added to global economic worry.
U.S. crude for January <CLc1> fell $1.46 to a low of $80.28 per barrel but then recovered some ground and by 1411 GMT was trading around $81, after losing 71 cents on Monday. ICE Brent <LCOc1> was down $1 at $82.96 a barrel.
Oil and commodities often move inversely to the dollar, partly because many of them are priced in the U.S. currency.
The euro came under further pressure as political uncertainty in Ireland and worries about other heavily indebted members of the 16-nation euro zone snuffed out optimism over a bailout plan for Dublin. [
] [ ]Analysts said the Korean shelling and Irish meltdown had come at a time when risk aversion could be expected to rise anyway ahead of the Thanksgiving weekend in the United States.
"REDUCTION OF RISK"
"We are in front of a very long weekend," Olivier Jakob at Petromatrix said. "Long weekends usually lead to short-covering, but the recent political uncertainties in Ireland and the military escalation between North and South Korea would plead for reduction of risk in front of the holidays."
"Given that the main area of growth is out of emerging Asia, the escalation of tensions between North and South Korea is not a positive development for oil markets," Jakob added.
Christopher Barret, global oil analyst at French bank Credit Agricole, said the flight to safety in financial markets could be hastened by end-year acounting by some funds.
"A lot of funds are clearing positions for reporting purposes at this time of the year anyway and this will encourage them to reduce exposure even more quickly," Barret said.
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For a map showing the loaction of the artillery exchange on the Korean peninsula, click: http://link.reuters.com/wyh76q
For a graphic of the components of Reuters Jeffries CRB Index of commodities, click: http://link.reuters.com/kew48n
For links to stories on Europe's debt crisis: [
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The European Union urged Ireland on Tuesday to adopt an austerity budget on time in order to receive an EU/IMF bailout despite calls for an immediate general election that could disrupt the rescue. [
]Expectations of a drawdown in U.S. crude stocks, reflecting demand in the world's top energy consumer, could support prices.
Industry data from the United States due at 2130 GMT is expected to show a third week of decline for crude inventories following a surprise heavy drawdown in the previous week, a Reuters poll showed on Monday. [
]The market is also keeping an eye on the political situation in Saudi Arabia as the country's ageing King Abdullah arrived in the United States for medical treatment on Monday, while a frail Crown Prince Sultan hurriedly returned from abroad to govern the world's largest oil exporter. [
] (Additional reporting by Florence Tan in Singapore; editing by Keiron Henderson)