US election 2016: Trump and Clinton remain front-runners
US presidential hopefuls Donald Trump and Hillary Clinton have maintained their status as front-runners in the latest round of voting for their parties' nominations.
Despite defeats to Ted Cruz in Kansas and Maine, Republican Mr Trump won in Louisiana and Kentucky.
Other Republican contenders Marco Rubio and John Kasich made little progress.
Mrs Clinton lost to Bernie Sanders in the Democratic races in Kansas and Nebraska, but won in Louisiana.
Texas Senator Cruz now appears to be the only candidate who can stop Mr Trump, analysts say, after a week in which the Republican establishment did everything it could to attack the New York tycoon.
At a glance:
- Donald Trump won two more states, bringing his total to 12
- Ted Cruz's two victories give him six wins in all
- Marco Rubio has won only one state, while John Kasich has none
- Hillary Clinton's win in Louisiana gives her a total of 11 states
- Bernie Sanders' two victories give him seven wins in all
Observers also point out that Mr Cruz and Vermont Senator Sanders both won in caucuses but lost in the Louisiana primary elections, involving far more voters.
The Democratic race in Louisiana - comfortably won by Mrs Clinton - also appears to have exposed Mr Sanders' lack of support among African-American voters.
Both Mr Trump and Mr Cruz urged the other Republican contenders to drop out of the race.
Speaking after his wins in Kentucky and Louisiana, Mr Trump told a news conference: "I would love to take on Ted Cruz one on one."
Mr Cruz suggested it was time for Senator Rubio and Ohio Governor Mr Kasich to step aside.
"As long as the field remains divided, it gives Donald an advantage," he said.
Saturday's voting story: By Anthony Zurcher, BBC News
Although Donald Trump has surged to a sizeable lead in the race for the Republican presidential nomination, there were two significant areas in which he had underperformed. He tended to struggle in caucuses and in states where voting is limited to members of the Republican Party.
Saturday's results confirmed that this will continue to be a challenge for the front-runner. He lost closed caucuses to Ted Cruz in Kansas and Maine, and posted a narrow win in Kentucky. He also edged Mr Cruz in Louisiana's closed primary.
Although there aren't many caucuses left on the Republican calendar, most of the upcoming primaries are closed - including the key vote in Florida in just over a week.
Saturday night's showing helped buttress Mr Cruz's argument that he is the party's best hope to challenge Mr Trump, as Marco Rubio and John Kasich continue to lag far behind. If the Texas senator is to catch the New York billionaire, however, loyal Republican Party voters, particularly in Florida, will have to rally behind him in even greater numbers. It's a tall task - but not an impossible one, if the once-popular Mr Rubio continues to haemorrhage support.
The Democratic results presented yet further evidence that Bernie Sanders can beat Hillary Clinton in smaller, more homogenous states, but she is likely to continue to extend her lead with big wins in Southern and ethnically diverse states, as she did in Louisiana on Saturday.
Mrs Clinton said she was thrilled to extend her lead over Mr Sanders in the delegate count.
She added: "No matter who wins this Democratic nomination, I have not the slightest doubt that on our worst day we will be infinitely better than the Republicans on their best day."
Her advantage among pledged delegates - those awarded according to how the states have voted - is substantially bolstered by the hundreds of so-called 'super delegates' who have said they will back her at the convention.
The election itself, on 8 November, will see America vote for a successor to Barack Obama, a Democratic president standing down after two terms in office which have seen the Republicans take control of both houses of Congress.
Election calendar: Next races
- 6 March: Maine caucuses: Democratic
- 8 March: Hawaii and Idaho caucuses: Republican; Idaho primary: Republican; Michigan and Mississippi primaries: Democratic and Republican
- 15 March: Florida, Illinois, Missouri, North Carolina, Ohio primaries: all Democratic and Republican