The revelation that U.S. President Donald Trump's most senior national security officials posted the specifics of a military attack to a chat group that included a journalist hours before the attack took place in Yemen has raised many questions.

Among them is whether federal laws were violated, whether classified information was exposed on the commercial messaging app, and whether anyone will face consequences for the leaks.

Top Trump administration officials texted a group chat including a journalist plans for strikes on Yemen's Houthi rebels, the White House said, an extraordinary security breach that shocked Washington's political elite.

U.S. President Donald Trump announced the strikes on March 15, but The Atlantic magazine's editor-in-chief Jeffrey Goldberg wrote on Monday that he had hours of advance notice via the group chat on Signal, which included Defense Secretary Pete Hegseth and Vice President JD Vance.

Denmark's foreign minister on Monday slammed as "inappropriate" a planned visit by a US delegation to Greenland -- a Danish autonomous territory coveted by U.S. President Donald Trump.

A Russian missile attack on a hospital and residential area in Ukraine's northeastern city of Sumy on Monday wounded 28 people, local officials said, as Moscow and Washington held talks in Saudi Arabia on a potential ceasefire.

"Today, the enemy attacked the residential neighbourhood and infrastructure facilities in the city, including children's institutions and a hospital," acting mayor of Sumy Artem Kobzar said, adding "24 adults and four children" were wounded.

As President Donald Trump and billionaire Elon Musk work to overhaul the federal government, they're forcing out thousands of workers with insider knowledge and connections who now need a job.

For Russia, China and other adversaries, the upheaval in Washington as Musk's Department of Government Efficiency guts government agencies presents an unprecedented opportunity to recruit informants, national security and intelligence experts say.

Iran said on Monday it was open to indirect talks with the United States, after President Donald Trump had issued an ultimatum for a new nuclear deal.

"The way is open for indirect negotiations," Foreign Minister Abbas Araghchi said, dismissing the prospect of direct talks with Washington "until there is a change in the other side's approach towards the Islamic republic".

Istanbul's embattled Ekrem Imamoglu was officially nominated as a presidential candidate by the opposition CHP party for the 2028 elections, a party spokesman told AFP on Monday.

The Republican People's Party (CHP) -- the main opposition party and the second largest party in parliament -- held a primary election on Sunday, at which the only candidate was Imamoglu, the main political rival of President Recep Tayyip Erdogan. Imamoglu has been arrested, interrogated, jailed and stripped of his mayorship in less than a week following a graft and terror probe that the opposition has slammed as a political "coup."

Turkish authorities detained several journalists from their homes, a media workers' union reported Monday, in what it said was a crackdown amid escalating protests triggered by the imprisonment of the mayor of Istanbul and top rival to President Recep Tayyip Erdogan.

On Sunday, a court formally arrested Mayor Ekrem Imamoglu and ordered him jailed pending a trial on corruption charges. His detention on Wednesday sparked the largest wave of street demonstrations in Turkey in more than a decade and deepened concerns over democracy and the rule of law in the country.

U.S. and Russian negotiators on Monday sat down for talks in Saudi Arabia on a partial ceasefire in Ukraine, hours after a round of negotiations between U.S. and Ukrainian delegations, Russian news reports said.

The state Tass and RIA-Novosti news agencies said the negotiations had begun in the capital Riyadh. The meeting is expected to be followed by another contact between U.S. and Ukrainian teams.

Donald Trump's Middle East envoy Steve Witkoff said the U.S. president was trying to head off armed conflict with Iran by building trust with Tehran.