* Oil up on Oct. futures expiry, U.S. rescue plan
* Saudi Arabia trims oil supply to majors
* Nigerian rebels declare unilateral cease-fire
* U.S. oil sector recovering from Ike (Updates prices with U.S. settlement)
By Joe Brock
LONDON, Sept 22 (Reuters) - Oil prices soared more than 15 percent on Monday -- the biggest one-day gain on record -- continuing a rally sparked by the expiry of the front-month futures contract and the United States' rescue plan for its financial sector.
U.S. crude for October delivery <CLc1>, which expires Monday, settled up $16.37, or 15.7 percent, at $120.92 per barrel. The contract for delivery in November, which was much more actively trade, was up only $6.62 at $109.37.
London Brent crude <LCOc1> traded up $5.84 at $105.45.
"Short squeeze, crude expiration -- that's it in a nutshell. The dollar did drop further today, but you'll note that the October-November crude spread blew way, way out," Tom Knight of Truman Arnold in Texas said.
Sweeping government measures to rescue the financial system and restore confidence in shaky markets spurred gains across markets on Friday, when oil rose almost 7 percent to cap its biggest three-day rally in a decade.
Oil had tumbled from record highs above $147 a barrel in mid-July, weighed down by growing evidence that high energy costs and economic woes were undercutting global fuel demand.
"The key driver continues to be the U.S. rescue package, which has changed the sentiment in the oil market," said Bank of Ireland analyst Paul Harris.
The slow recovery of the U.S. oil sector after Hurricane Ike also supported prices, after causing the biggest disruption to the nation's energy supplies since 2005.
Nearly 80 percent of oil production in the U.S. Gulf of Mexico, home to a quarter of all U.S. oil output, remained shut along with seven refineries. [
]Oil prices were also supported by news China increased crude imports 11.54 percent in August from a year earlier, recovering from a steep July fall, the General Administration of Customs said on Friday, confirming earlier data. [
]"The Chinese import news is a sign of recovery, and a good indication that oil prices could get back up again," said Christopher Bellew of Bache Financial.
Industry sources also said on Monday that top oil exporter Saudi Arabia has trimmed oil supplies to major international oil companies and U.S. refiners since the start of September. [
]However, gains were capped by news that Nigeria's main militant group had begun a unilateral cease-fire on Sunday, after a week of clashes with the military and attacks on oil installations that cut output in Africa's top producer. [
] (Reporting by Joe Brock, Matthew Robinson, David Sheppard in London; Fayen Wong in Perth; Richard Valdmanis in New York; Editing by Walter Bagley)