JUBA: South Sudan hopes boost crude production by close to 50 percent by June, its oil minister said on Monday, targeting an increase that one observer called optimistic as the country edges towards forming a national unity government.

Output was about 350,000-400,000 barrels per day (bpd) up to 2013, when a five-year civil war broke out.

Production currently stands at around 160,000 bpd and that should rise by 70,000 bpd by June, Minister of Petroleum Ezekiel Lol Gatkuoth said.

"With 3.5 billion (barrels of) proven reserves and only 30 percent explored, there is more to offer to serious investors," he said in a statement while attending a conference in Equatorial Guinea.

He said production would restart in the Al-Nar, Al-Toor and Manga oilfields by April 27.

Global energy consultancy firm Wood Mackenzie forecast a  far more modest rise to over 170,000 bpd by 2020, although it said if the peace deal lasted that could rise to 230,000 bpd.

"We assume this will be done by re-opening shut-in wells, workovers and repairs. To increase production beyond this would need significant capital expenditure, which the operators will be wary of until political stability is properly established," a strategy paper it published in September 2018 said.

The firm said on Monday it stood by its forecast.

Much of the landlocked East African nation's oil infrastructure was damaged in the war, during which about 400,000 people were killed and more than a third of the country's 12 million population uprooted.

The conflict was punctuated by multiple rounds of failed mediation followed by renewed bloodshed.

The government signed a peace deal with the main rebel group in September, under which they were to gather, disarm, retrain and integrate their forces ahead of the formation of a government of national unity in May.

But that has not yet happened. One group led by former deputy army chief Thomas Cirillo refused to sign and has continued to launch attacks. Last month, the International Crisis Group - an independent research body - said the deal was at risk of collapse.

The United States has imposed sanctions on many individuals and businesses over what it says are widespread corruption and human rights abuses under President Salva Kiir.

Kiir, who is also due to head the new government, denies any wrongdoing.