Oil prices rose and stocks fell Friday as the United States and Israel struck Iranian nuclear sites, denting optimism over potential talks to end nearly a month of war in the Middle East.

US President Donald Trump has extended a deadline for Tehran to open the Strait of Hormuz or face the destruction of its energy grid, pushing it from Friday to April 6.

But with Iran maintaining a hold on the strait and intense hostilities continuing, Trump's announcement failed to lift the mood on markets.

Oil prices climbed, with the Brent international benchmark rising 4.2 percent to $112.57 while the US benchmark contract, WTI, jumped 5.5 percent to $99.64.

Wall Street stocks fell sharply across the board, with the the S&P 500 ending the week lower for the fifth straight week, its longest such run in four years.

European and Asian stock markets also ended the day mostly lower.

The market reaction Friday contrasted sharply with the plunge in oil prices and gains for stocks at the beginning of the week after Trump first delayed his Hormuz deadline.

"Trump appears to be losing his grip on the markets," said Forex.com analyst Fawad Razaqzada.

"Investors no longer seem to take his statements at face value -- if anything, they're beginning to trade against them, waiting for tangible proof before reacting," he said.

Kathleen Brooks, research director at XTB, said: "Investors are facing the facts: the Strait of Hormuz is effectively closed and it does not appear that there is a real end in sight to the war."

Angelo Kourkafas, investment strategist at Edward Jones, said investors were concerned that sharply higher oil prices would have a significant impact on inflation and economic growth.

"There are concerns about the lingering uncertainty," Kourkafas said. "And as we have broken some technical levels, I would say that is triggering some more selling."

Trump has insisted that Iran wants to make a deal to end the war, despite Tehran denying his statements. US and Israeli strikes have continued, as has Iran's retaliation against across the Gulf.

"The simple fact is that sentiment is likely to stay negative for as long as the Strait of Hormuz remains unsafe for shipping and controlled by Iran," said David Morrison, an analyst at Trade Nation.

Adding to market woes, China on Friday opened an investigation into US trade practices in response to Washington's probes this month of Chinese exports.

Tokyo's stock market closed lower, while Hong Kong and Shanghai edged up.

Investor doubts about the chance of a peace deal came as governments around the world looked to shore up their economies against surging energy costs, which are adding to inflationary pressures.

Vietnam temporarily waived an environmental levy on fuel to cut petrol prices by more than a quarter, India said it had lowered fuel taxes, and Japan is looking to temporarily lift restrictions on coal-fired power plants in a bid to ease an energy crunch.