Friday's seizure came as tensions between the U.S. and Iran have increased since President Donald Trump's decision last year to pull the U.S. from Iran's nuclear accord with world powers and reinstate sweeping sanctions on Iran.
The benchmark U.S. crude oil contract added 73 cents to $56.36 a barrel in electronic trading on the New York Mercantile Exchange. Brent, the international standard, rose 96 cents to $63.43 per barrel.
In Europe, France's CAC 40 edged 0.2% higher to 5,562, while Germany's DAX also gained 0.2% to 12,284. Britain's FTSE 100 gained 0.4% to 7,537. U.S. shares were also set to open higher, with Dow futures adding 0.2% to 27,188 and S&P 500 futures picking up 0.3% to 2,985.
In Asia, prices of many of the 25 tech companies listed on the Shanghai Stock Exchange's new STAR Market more than doubled in their debut, with one company, Anji Microelectronics Technology (Shanghai) Co., Ltd., logging a 400% advance.
Regulators have approved 25 companies in information technology and other fields for the STAR Market. The market, modeled on the U.S.-based NASDAQ, reflects the ruling Communist Party's desire to channel private capital into its development plans. It gives small Chinese investors a chance to buy into tech industries that until now have turned to Wall Street to sell shares.
Elsewhere in Asia the mood was more subdued. Japan's Nikkei 225 slipped 0.2% to finish at 21,416.79. Australia's S&P/ASX 200 fell 0.1% to 6,691.20. South Korea's Kospi edged less than 0.1% lower to 2,093.34. Hong Kong's Hang Seng dipped 1.4% to 28,371.26, while the Shanghai Composite index shed 1.3% to 2,886.97.
News that the Chinese government has decided to allow full foreign ownership of securities, fund management and futures companies next year, one year earlier than previously planned, did not help lift shares in Shanghai.
A weekend Cabinet announcement also promised to increase the limit on foreign ownership of insurance companies from 25% and to open pension and asset management to foreign competitors. It gave no timetable or other details.
Washington and other trading partners complain Beijing is dragging its feet on promises to open its financial industries after it joined the World Trade Organization in 2001. Business groups have welcomed industry-opening steps promised over the past 18 months but say foreign competitors need to see licensing and other restrictions before they can know whether operations might be profitable.
On Friday, U.S. stocks retreated further from their records to cap the weakest week for the S&P 500 since May. Momentum for U.S. stocks has slowed since early June, when they began soaring on expectations that the Federal Reserve will cut interest rates for the first time in a decade to ensure the U.S. economy doesn't succumb to weaknesses abroad. The Fed's next meeting is scheduled for the end of this month. The European Central Bank will meet Thursday and some analysts say it could cut interest rates.
"Investors could remain singularly focused on the Federal Reserve, and the European Central Bank policy decision and communications as global equity markets continue to have their ups and down based on the perceived degree of accommodative central bank policy," Stephen Innes of Vanguard Markets said in a commentary.
In currencies, the dollar rose to 107.93 Japanese yen from 107.74 yen on Friday. The euro weakened to $1.1218 from $1.1221.
Ott reported from Washington. Joe McDonald in Beijing also contributed to this report.