The World Health Organisation says the Democratic Republic of Congo has begun the first-ever trial to test the effectiveness and safety of four experimental Ebola drugs, the first time scientists have directly compared such treatments.

In a statement on Monday, the UN health agency described it as "a giant step" that would "bring clarity about what works best". To date, more than 160 people have been treated with these experimental drugs. Patients won't be treated much differently than before, but scientists will now have a clinical trial framework to collect data.

The drugs being tested are three antibody treatments and an antiviral. So far in the current outbreak in DRC, there have been 346 confirmed Ebola cases and 175 deaths.

The outbreak has been plagued by security problems, with some health workers attacked by rebels.