Donald Trump said on Sunday the US military has killed Jamal al-Badawi, an al-Qaida militant wanted in connection with the attack on the USS Cole.

Seventeen US sailors died and at least 40 people were wounded in the October 2000 attack, in which suicide bombers almost sank the guided missile destroyer while it lay in Aden harbour.

The attack on the USS Cole foreshadowed the attacks of 11 September 2001, in which 2,977 people were killed in New York City, Washington DC and Pennsylvania. Badawi was indicted in 2003 and charged with terrorism offences including the murder of US nationals and military personnel. He escaped from prison in Yemen twice, once in 2003 and again in 2006. There was a $5m reward for information leading to his arrest.

It was reported on Friday that US defence officials were trying to confirm reports an airstrike on 1 January had killed Badawi. On Sunday, via Twitter, the president confirmed it.

“Our GREAT MILITARY has delivered justice for the heroes lost and wounded in the cowardly attack on the USS Cole,” the president wrote, while en route from the White House to Camp David. “We have just killed the leader of that attack, Jamal al-Badawi. Our work against [al-Qaida] continues. We will never stop in our fight against Radical Islamic Terrorism!”

Two hours later, US Central Command issued a tweet of its own, saying it had “confirmed that Jamal al-Badawi was killed in a precision strike in Marib governate [on 1 January]. Jamal al-Badawi was an [al-Qaida] operative involved in the USS Cole bombing. US forces confirmed the results of the strike following a deliberate assessment process.”

The news came amid further turmoil in the US defense establishment, which in the past month has digested the resignations of defense secretary Jim Mattis and envoy Brett McGurk over Trump’s abrupt decision to declare the fight against Islamic State militants won and to order the withdrawal of troops from Syria.

National security adviser John Bolton seemed to be walking back that order in a visit this weekend to Israel and Turkey, but at home in Washington another key Pentagon figure, chief of staff Kevin Sweeney, announced his resignation.

In a short statement on Saturday night, the retired Rear Admiral said: “After two years in the Pentagon, I’ve decided the time is right to return to the private sector. It has been an honor to serve again alongside the men and women of the Department of Defense.”

Citing an anonymous source, CNN reported on Sunday that Sweeney had been “forced out”.

On Saturday night, Samantha Power, ambassador to the United Nations under Barack Obama, tweeted: “We have no Secretary of Defense & now no DoD chief of staff, no Attorney General & no evident guardrails in Trump’s inner circle. The President is unhinged – even GOP zealots know it. Rs inside & outside the admin must stop enabling Trump & protect America.”

Appearing on CNN’s State of the Union on Sunday, California Democrat and House intelligence chair Adam Schiff said of Power’s tweet: “I largely do agree that all of the adults are one by one being forced out of the room. Anyone who had the standing … to tell the president what he needed to hear, not what he wanted to hear, has been pushed aside.”

It was not immediately clear if Trump’s announcement of the death of al-Badawi had been cleared by the acting defense secretary, former Boeing executive Patrick Shanahan, or any other senior official.