Oil prices rebounded Monday in Asia on comments by Iran's president suggesting a significant increase in the country's nuclear programme, but worries about the faltering US economy and crude demand continued to weigh on futures.

Light, sweet crude for September delivery rose $1.37 to $124.63 a barrel in Asian electronic trading on the New York Mercantile Exchange by mid afternoon in Singapore.

The contract fell $2.23 to settle at $123.26 a barrel on Friday - oil's lowest point in weeks - as investors questioned whether crude has cooled enough to reflect a serious deterioration in demand.

But Iranian President Mahmoud Ahmadinejad's announcement on Saturday that Iran now possesses 6,000 centrifuges raised concerns about an increase in tensions between Western powers and OPEC's second-largest producer over its nuclear programme.

The higher number, which is double the 3,000 uranium-enriching machines Iran had previously said it was operating, is certain to further rankle the United States and others who fear Tehran is intent on developing weapons.

"The comments by the Iranian president are a reminder that the Iranian situation remains fluid," said Victor Shum, an energy analyst with consulting firm Purvin & Gertz in Singapore.

In Nigeria, eight foreign oil workers who were kidnapped at gunpoint by six unidentified men in a speed boat on Saturday were released unharmed hours later, according to a Nigerian military spokesman. 

The abduction highlighted the risks of operating in the African nation, a major supplier to the US. Earlier in the week, Nigerian militants threatened to blow up pipelines in the region within a month.