Ukraine conflict fear and Pardew headbutt in the papers
Concerns are expressed in Sunday's newspapers about Moscow's military deployment in Crimea, with many carrying pictures of Russian troops in the territory on their front pages.
According to the Observer, the announcement came "suddenly and decisively". But it also reports the Kremlin's assertion that President Putin wanted to introduce troops into Ukraine "until the sociopolitical situation is normalised".
"Western leaders... have hardly been impressive in their response, demonstrating a weak grasp on the events unfolding. For now, Putin is ahead of the game. It is time for the international community to catch up."
The Independent says the announcement "after days of sabre rattling has caused a schism in international relations that threatens to reopen the Cold War, after the West repeatedly warned Russia against military intervention".
Writing in the same paper, the UK's former Moscow ambassador Rodric Braithwaite suggests a diplomatic response may fall on the Germans, the Poles and the French, since the "Americans are being ineffective on the sidelines, and the British seem to have given up doing foreign policy altogether".
The Sunday Times correspondent in Crimea is among those to portray the standoff as "increasing tense".
But Askold Krushelnycky writes that a "curious mix of menace and normality reigned", describing the sight of a wedding convoy winding its way through a hastily built Russian military checkpoint in Sevastopol.
The Observer is among the papers to highlight the groups in Ukraine who have come out in support of President Putin, among them the motorcycle gang the Night Wolves.
Observer correspondent Harriet Salem writes: "They say they are ready to defend Crimea against all unwanted intrusions, namely Western authorities and the new administration in Kiev, seen by many in the region as bandits and terrorists who seized power illegally."
The cartoonists also interpret the situation.
The Independent on Sunday's Peter Schrank has a bare-chested Russian President Vladimir Putin in combat pants lying across the cannon of a tank and proclaiming: "This is my principled position of non-intervention".
Steve Bright in the Sun on Sunday contrasts a suited President Putin surrounded by athletes at the Sochi Winter Olympics with him in a tank clutching an assault rifle. "A week is a long time in politics," it says.
And ahead of the Oscars ceremony, Gerald Scarfe in the Sunday Times expresses what many commentators appear to be thinking when he portrays the Russian president in military garb standing astride a map of Crimea, with the caption "Best actor? - or for real?"
A call on David Cameron to stave off the threat from UKIP by adopting a radical plan to curb the number of low-skilled immigrant workers is carried in the Sunday Telegraph.
In an article for the paper, former defence secretary Liam Fox warns the prime minister would be guilty of "dangerous complacency" if he failed to address the potential election damage.
"The correct response is to set out a positive vision, clear philosophy and definable objectives," Mr Fox says, urging the party to ditch the "statistical nonsense" of concentrating on reducing net migration numbers.
Grandees from "opposite ends of the party" have more advice for Mr Cameron on dealing with UKIP, the Sunday Times says.
Former Deputy Prime Minister Lord Heseltine suggests moving to the right could alienate moderate supporters, while ex-party leader Lord Howard says Mr Cameron should not to pander to UKIP's agenda and instead target wavering Lib Dem voters.
There's a warning too for Labour leader Ed Miliband in the Sunday Mirror on relying too much on UKIP taking votes away from the Tories.
"Disaffected Tories who switch to UKIP could put Labour in power but that's not how Ed Miliband should reach No 10," it says in an editorial. "He needs to win on merit."
The Sunday Mirror also reports that former Labour Foreign Secretary Lord Owen has made a "surprise return to the fold" with a £7,500 donation to the party. The pledge from the co-founder of the breakaway Social Democrats came as Mr Miliband won backing for his plans to change the Labour's links with the unions.
The support from Lord Owen is seen by the Sunday Times as a sign that Mr Miliband will be able to "appeal to influential figures who were once alienated by the unions' power" over Labour.
'Draw a line'
A range of other political stories make headlines.
British troops involved in the Bloody Sunday killings in 1972 should escape prosecution, former Northern Ireland Secretary Peter Hain says in an article for the Sunday Telegraph.
Amid the controversy over the disclosure that a number of suspected IRA terrorists had been given effective immunity from prosecution as part of the Northern Ireland peace process, Mr Hain said it was time to "draw a line on historic and in all probability fruitless investigations" for the sake of future generations.
Labour plans for school pupils to study maths and English up to the age of 18 are revealed in the Observer. The move will bring England and Wales in line with most developed countries, where such key subjects are compulsory until students leave school, the paper says.
The Mail on Sunday follows up reports that Boris Johnson has been urged to demonstrate his "loyalty" to the Tories by standing as an MP at the next election.
It says the London mayor denies such an approach had been made, with supporters saying the stories were part of a "plot" to wreck his hopes of becoming party leader in future. Sources close to the mayor, however, later played down reports of a feud between Mr Johnson and Chancellor George Osborne.
A report from a campaign group which says 2,653 young people were referred to government-funded de-radicalisation programmes between 2006 and 2013, including a nine-year-old schoolboy in east London, is the lead story in the Daily Star Sunday.
The Sunday People reports that the Home Office have launched an investigation into claims that a civil servant in the department approved grants of about £70,000 to the Paedophile Information Exchange between 1977 and 1980. The disbanded group is at the centre of controversy over its links with the National Council for Civil Liberties at the time.
'Premier League shame'
Former Tottenham and Arsenal defender Sol Campbell has told the Sunday Times he would have been the first-choice England captain for 10 years had he been white.
In extracts from his new biography, serialised in the paper, Campbell said he "had the credibility, performance-wise, to be captain. I was consistently in the heart of the defence and I was a club captain early on my career".
The player, who did captain the side three times, was speaking out in an attempt to make sure the same situation does not arise in future.
Staying with football, there is much focus on Newcastle United manager Alan Pardew after he headbutted Hull City midfielder David Meyler.
Pardew was later fined £100,000 by his club and given a formal warning.
The Sunday Telegraph says for Pardew the incident at the KC Stadium was the "most serious in a long history of touchline offences" and he is "certain" to receive a further fine from the Football Association.
Calls by former club managers Alan Shearer and Graeme Souness for Pardew to leave the Magpies are reported in the Sunday Express.
Pardew reacted after Meyler shoved past him in an attempt to retrieve the ball to take a throw-in and has since apologised for his actions.
The "moment of madness", as the Mail on Sunday describes it, saw the referee send Pardew to the stands to watch the rest of the match.
But the Mail reckons he could now face a touchline ban for the rest of the season as a consequence of the "outrageous" bust up.
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