LONDON (Bloomberg) -- Crude oil rose for a second day, exceeding $71 a barrel, as Nigerian militants continued attacks on oil installations in Africa’s largest crude producer.

Militants in Nigeria said on Friday they attacked the second well head at Royal Dutch Shell Plc’s Afremo offshore oil field last night. The Movement for the Emancipation of the Niger Delta said on Thursday they attacked a Shell pipeline supplying an export terminal. A weaker dollar also boosted oil as an alternative investment.
“For oil, it’s largely the dollar and persistent attacks in Nigeria,” Andrey Kryuchenkov, a VTB Capital commodity analyst in London, said by phone. “I don’t think it’ll go higher from here. It’ll sit here below $72.”
Crude oil for August delivery rose as much as $1.06, or 1.5 percent, to $71.29 a barrel in electronic trading on the New York Mercantile Exchange. It traded at $71.22 a barrel at 10:31 a.m. London time.
Shell’s offshore facility was blown up at about 11 p.m. on Thursday, hours after an offer of an amnesty by President Umaru Yar’Adua. The attack was in response to “a punitive” raid by the military on the Agbeti community in the Delta state, the main oil-producing region.
The platform had been shut since Feb. 28 following an attack on Shell’s Trans Escravos Pipeline, Precious Okolobo, Shell’s spokesman in Nigeria, said by phone. Military spokesman Colonel Rabe Abubakar said troops didn’t carry out any raids on Thursday.
“The factor supporting oil is the situation in Nigeria,” said David Moore, a commodity strategist with Commonwealth Bank of Australia Ltd. in Sydney. “It seems to have intensified and it’s something that’s helping keep prices at a higher level.”
Oil has gained 2.3 percent this week after falling 3.5 percent last week.
-------------Brent crude
Brent crude oil for August settlement rose as much as $1.03, or 1.5 percent, to $70.81 a barrel on London’s ICE Futures Europe exchange. It traded at $70.65 a barrel at 10:32 a.m. in London and is up 6 percent this week.
A falling dollar makes raw materials such as oil and gold an attractive alternative investment. The dollar traded at $1.4041 versus the euro at 9:59 a.m. in London from $1.3988 on Thursday.
Oil prices have been supported and supply curbed since the re-emergence of militant activity in the Niger River delta, Nigeria’s main oil-producing region, in December 2005. MEND has stepped up a sabotage campaign in the area since a military offensive began last month.
Fighters from the Nigerian group damaged the Bille-Krakrama pipeline, cutting supplies from Shell’s Cawthorne 1, 2 and 3 oil-pumping stations, MEND spokesman Jomo Gbomo said in an e- mail on Thursday. A Shell spokeswoman confirmed an attack on a manifold on the pipeline and couldn’t say whether production was halted by the incident.
Nigeria produces so-called sweet, or low-sulfur, crude oil that is prized by refiners because it yields a large amount of gasoline and diesel fuel when processed.