The front-runners for the nominations in the US presidential race are aiming to extend their leads on Saturday (Sunday morning in Nigeria).

Republicans are holding caucuses or primaries in four states, with Democrats voting for their candidate in three.

Former Secretary of State Hillary Clinton leads the Democrats’ contest while billionaire Donald Trump is ahead in the Republicans’ race.

Efforts by Republicans to slow Mr Trump’s march have so far failed.

At a televised debate on Thursday, his main rivals for the nomination, Ted Cruz and Marco Rubio, launched a series of attacks on him.

Mitt Romney, the 2012 Republican nominee, earlier accused the businessman of bullying, greed and misogyny. Mr Trump dismissed Mr Romney as a “failed candidate”.

Two days earlier, on Super Tuesday, Mr Trump won seven of the 11 contests.

At Saturday’s caucuses in Kansas, Kentucky and Maine, as well as the Louisiana primary, Mr Trump will be seeking to cement his lead.

The more states pick him, the more delegates he claims. Republican candidates need 1,237 delegates to win the nomination.

Mr Trump is 908 delegates short; 155 are available on Saturday. (BBC)

•Photo shows US presidential aspirants.