US Defence Secretary Pete Hegseth shared information about US air strikes on Yemen in a second private group on the Signal app, the BBC's US partner CBS has confirmed with sources familiar with the messages.

The messages, sent on 15 March, included flight schedules for American F/A-18 Hornets carrying out strikes on Houthi targets. The group included Hegseth's wife, brother and personal lawyer.

The developments come a month after the existence of a separate Signal group discussing sensitive information about US military operations was revealed.

In a statement to the New York Times, which first reported the second group, the White House said no classified information was shared.

Hegseth's wife, Jennifer, is a former Fox News producer and holds no official position within the Pentagon. Hegseth has previously been criticised for reportedly including his wife in meetings with foreign leaders.

His brother, Phil, and personal lawyer, Tim Parlatore, both hold positions at the Department of Defense. But it is not clear why any of the three would require advanced warnings of sensitive US strike plans.

Unlike the first Signal group, the second one - called "Defense | Team Huddle" - was created by Hegseth, according to the New York Times.

The existence of the earlier Signal group was revealed by Jeffrey Goldberg, the editor of the Atlantic magazine, who was accidentally included in it. Officials similarly used that group to discuss information relating to strikes in Yemen.

The White House denied that classified information was discussed in that group either, although critics of Hegseth - including former US defence officials - question that. They say discussing such information in Signal groups could jeopardise US personnel carrying out military operations.

The existence of the second Signal group is the latest controversy surrounding the head of the Pentagon, who this year is controlling a budget of $892bn (£670bn).

Hegseth last week fired three top officials for an "unauthorised disclosure" - an accusation the officials said was "baseless".

In an op-ed for Politico magazine published on Sunday, John Ullyot, a former top Pentagon spokesperson who resigned last week, wrote that the department was in "total chaos".

"The dysfunction is now a major distraction for the president - who deserves better from his senior leadership," Ullyot added.

However, in a statement on X, Sean Parnell, current chief spokesman for the Pentagon, accused the "Trump-hating media" of "destroying anyone committed to President Trump's agenda".

He echoed the White House by saying that "there was no classified information in any Signal chat".

Washington says its strikes in Yemen are punishment for Houthi attacks on cargo vessels transiting through the Red Sea, a critical waterway for international trade.

Since November 2023, the Houthis have targeted dozens of merchant vessels with missiles, drones and small boat attacks in the Red Sea and the Gulf of Aden. They have sunk two vessels, seized a third, and killed four crew members.

The Houthis have said they are acting in support of the Palestinians in the war between Israel and Hamas in Gaza, and have claimed - often falsely - that they are targeting ships only linked to Israel, the US or the UK.

US air strikes on an oil terminal in north-western Yemen this week killed at least 74 people and wounded 171 others, according to the Houthi-run health ministry. The Houthi-led government said the attack constituted a "war crime".