The letter, sent on Sunday, amounts to the strongest known written warning from the US to its ally.
The BBC finds gang warfare in jails is rife, and lack of space makes it difficult to keep rivals apart....
The nurse was described as "lacking the natural warmth" and empathy needed to care for children....
Could the US election result threaten support for Kyiv?...
The Witches of Bucha, as they call themselves, help protect Ukraine's skies from Russian drones....
A public inquiry examining the death of Dawn Sturgess has heard evidence from the former Russian spy....
The UK is losing out because of cuts to the World Service, the BBC's director general warns....
The South Caucasus nation of Georgia has a huge used car market, with many vehicles finding their way over the border....
The BBC visits a key city under attack by Russia and finds eroded morale among its few remaining residents....
Kyiv's human rights ombudsman has written to the UN, after reports that Russia executed Ukrainian PoWs....
Viktoriia Roshchyna had been detained last year while reporting in Russian-occupied Ukraine....
Wigan Warriors become the first side in the Super League era to win all four trophies in a single season, beating Hull KR in a tight Grand Final at Old Trafford....
After winning an unprecedented quadruple in the Super League era, are Wigan Warriors the greatest ever side?...
Wigan Warriors seal the quadruple and become the first side to win all four trophies in a season as they beat Hull KR in the Super League Grand Final....
Donald Tusk said Russia and Belarus were encouraging migration into Poland in a bid to destabilise the EU....
The ex-Wallabies captain was given a five-year sentence for embezzlement in France, local media say....
Giora Eiland tells Jeremy Bowen that Israel should tell Palestinians to leave northern Gaza before sealing it off as a way of pressuring Hamas....
The Russian opposition leader's posthumous memoir traces his final years, including his captivity....
A shipping company shelving a major investment and Russian hackers attacking UK ambulance services feature in the papers....
Three venomous scorpions have been found in parcels in the UK in the last month, expert Chris Newman says....
The ongoing Israel-Hamas war broke out 12 days before the girl was to receive treatment in Jerusalem....
Ukrainians watched intrigued as a Russian stealth combat drone was apparently shot down by a Russian jet....
The Premier League has warned its clubs it will be "taking the necessary time" to decide how to respond to the verdict in the landmark legal case with Manchester City over the rules governing commercial deals....
Robyn was born five months early and put in a sandwich bag to keep her organs warm while she grew....
Is this weekend's WXV1 decider between Canada and England in Vancouver the dress rehearsal for next year's Rugby World Cup final?...
Ahmed Abdirahman, 31, was charged in Dublin after Mary Ward's body was found in Belfast last week....
The economy grew by 0.2% but there is a warning that the "broader picture" is one of "slowing growth"....
Saturday's Super League Grand Final opponents Wigan Warriors and Hull KR offer a blueprint for success on and off the field....
The envelope addressed to a 'well-known historian' contained anecdotes from World War Two....
After Marina Perederii fled her home in Ukraine, it appeared in an online video of a Russian soldier looking through her photos....
The government is investigating 37 companies - but has yet to hand out any fines, the BBC discovers....