New York's main contract, light sweet crude for delivery in April, rose 58 cents to close at 98.81 dollars a barrel.
In London, Brent North Sea crude for April delivery settled up 77 cents at 97.01 dollars a barrel.
Oil prices had pulled back on Thursday, a day after spiking to a record high of 101.32 dollars, as supply concerns eased on a US government report that showed a bigger-than-expected build-up in US crude-oil stockpiles, the sixth weekly increase in a row.
The US inventory increase helped defuse market speculation that the Organization of the Petroleum Exporting Countries, which produces about 40 percent of the world's oil, may cut output at its March 5 meeting in Vienna.
Demand bears pointed to the rapidly deteriorating economic conditions in the United States, the world's largest energy consumer, and their effect on overall global demand.
Analysts are divided over whether the world's biggest economy is entering recession or already in it, and factoring in rising inflation, largely driven by higher oil prices.
"As the economy slows and commodities fly, talk of stagflation is all the rage!" said Phil Flynn at Alaron Trading.
Mike Fitzpatrick of MF Global said the weakening fundamental environment for oil means "a more direct threat to supplies will probably be required for the market to sustain a move over 100 dollars."
"It is hard to justify a 100-dollar-a-barrel price in an environment where both inventories and recessionary fears are rising," he said.
News of the Turkish incursion added to supply concerns Friday. Turkish troops entered northern Iraq late on Thursday to crack down on separatist Kurdish rebels after fighter jets struck at their bases.
"Oil futures were higher after Turkey's military announced they had initiated a land offensive backed up by fighter jets into northern Iraq," said Sucden analyst Nimit Khamar.
"These fresh geopolitical developments brought oil futures back into positive territory."
Barclays Capital analyst Kevin Norrish dismissed the impact of the incursion on supply lines.
"While getting more overt and increasing in scale, the dynamics of the dispute do not seem to have changed particularly and in our view they are more illustrative of the instability of regional politics in north Iraq rather than posing any direct threat to oil flows in the regions," Norrish said