BERLIN (AP) -- Volkswagen CEO Martin Winterkorn stepped down Wednesday, days after admitting that the world's top-selling carmaker had rigged diesel emissions to pass U.S. tests during his tenure.
In a statement, Winterkorn took responsibility for the "irregularities" found in diesel engines but said he was "not aware of any wrongdoing on my part."
"Volkswagen needs a fresh start - also in terms of personnel," he said. "I am clearing the way for this fresh start with my resignation."
Volkswagen CEO Martin Winterkorn addresses the shareholders during the annual shareholder meeting of the car manufacturer Volkswagen in Hannover, Germany, Tuesday, May 5, 2015. (AP Photo/Frank Augstein)
Winterkorn's statement followed a crisis meeting of the Volkswagen supervisory board's executive committee. Its acting chairman, Berthold Huber, told reporters moments later that company directors are "resolved to embark with determination on a credible new beginning."
There was no immediate decision on a new CEO. Huber said that will be discussed only at a board meeting on Friday.
Winterkorn said VW must continue providing "clarification and transparency."
"This is the only way to win back trust. I am convinced that the Volkswagen Group and its team will overcome this grave crisis," he added.
VW shares were up 8.7 percent at 121 euros following his resignation.
The share price still has a long way to go to recoup the nearly 25 billion euros (around $28 billion) wiped off its market value in the first two days of trading after the U.S. Environmental Protection Agency announced that VW is violating the Clean Air Act.
Winterkorn, VW's boss since 2007, had come under intense pressure since the disclosure that stealth software makes VW's 2009-2015 model cars powered by 2.0-liter diesel engines run cleaner during emissions tests than in actual driving.
The EPA accused VW of installing the "defeat device" in 482,000 cars sold in the U.S. VW then acknowledged that similar software exists in 11 million diesel cars worldwide.
Huber said that "Mr. Winterkorn had no knowledge of the manipulation of emission values" and praised the departing CEO's "readiness to take responsibility in this difficult situation for Volkswagen."
Before the scandal broke, Winterkorn, 68, had been expecting to get a two-year contract extension, through 2018, at Friday's board meeting.
His resignation came only a day after he issued a video message asking staff and the public "for your trust on our way forward."
The EPA said Volkswagen AG could face fines of as much as $18 billion. Other governments from Europe to South Korea have begun their own investigations, and law firms have already filed class-action suits on behalf of customers.
VW directors renewed pledges of a thorough investigation after Winterkorn's resignation.
"We will clear up these events with all the possibilities we have inside the company and ensure that those involved are punished severely," said Stephan Weil, the governor of Lower Saxony state, which holds a 20 percent stake in Volkswagen.
Weil added that the company itself would file a criminal complaint, "because we have the impression that criminally relevant actions may have played a role here."
The prosecutors' office in Braunschweig, near VW's Wolfsburg headquarters, said earlier Wednesday that they are collecting information and considering opening an investigation against employees of VW who might be responsible.
Prosecutors said they already received "several" criminal complaints. Anyone can file a criminal complaint in Germany, and prosecutors must decide whether to act on them.