Italy's Eni, the European company with the largest presence in Libya, said it has begun flying out "non-essential personnel" and the families of its employees, The New York Times reports.
Germany's Wintershall, BP and Royal Dutch Shell are also preparing to evacuate staff or suspend exploratory drillings, the companies said in statements.
Wintershall, the oil exploration unit of chemicals giant BASF, Monday said it was preparing to fly some 130 people and their families out of Libya, where clashes between anti-government protesters and authorities have been raging for days and resulted in the deaths of more than 200 people.
Other companies, including ExxonMobil from the United States and Russian energy giant Gazprom, have stakes in Libyan oil and gas fields.
There is widespread concern that the country could descend into civil war, which would threaten energy exports to Europe.
One of Gadhafi's sons, Saif al-Islam Gadhafi, in remarks on state television said the protesters with their demonstrations were essentially "burning" Libya's oil wealth, warnings that didn't go unnoticed.
The price of Brent crude, a key benchmark for oil traded in London, rose to $104.60 a barrel in Monday trading, the highest level since 2008.
"We're concerned, and of course we'd like to see a solution sooner rather than later," Jason Kenney, an analyst with ING Financial Markets, told The New York Times. "It's very difficult to see how this is going to go. The oil price will be volatile."
Much of the Libya oil production is centered in the eastern part of the country, the location of the most violent clashes and a region where the government might lose control.
Libya's oil production stood at 1.58 million barrels per day in January, making it the seventh-largest producer in the Organization of Petroleum Exporting Countries, The Wall Street Journal reports.
Saudi Arabia, which has roughly double the output in spare capacity per day, could cover a fallout from Libya, observers say.
There is concern, however, that the unrest could spread further across the Middle East, certainly to Iran, and possibly, but not likely, to Saudi Arabia itself.