* Ouattara wants reinforced UN mandate
* UN evidence of "massive" rights abuses, hundreds abducted
* EU, US sanctions threatened within days
(Recasts adding EU sanctions, Choi, cocoa update)
By Tim Cocks and Ange Aboa
ABIDJAN, Dec 20 (Reuters) - Ivory Coast presidential claimant Alassane Ouattara urged the United Nations to toughen its peacekeeping mandate on Monday to help quell a violent power struggle that has already claimed over 50 lives.
Incumbent Laurent Gbagbo has defied pressure to step down after a Nov. 28 election the outside world says he lost, and his supporters have vowed to fight to the death after U.N. and French troops rejected his demand to quit the country.
In Brussels, diplomatic sources said European Union states had agreed that Gbagbo and 18 others would face punitive measures to be formally announced on Wednesday, and seen including travel bans and asset freezes.
U.N. Security Council powers are to review terms under which the 10,000-strong UNOCI peacekeeping force, whose current mandate runs out at the end of the month, will continue its presence in the world&${esc.hash}39;s top cocoa grower.
"I am in no doubt that it will be renewed," Patrick Achi, a spokesman for a rival Ouattara presidency that has set up base at a UN-guarded hotel in central Abidjan, said of Security Council discussions on the mandate due later on Monday.
"The question is ... will they change it to an intervention mandate to support the president -- that&${esc.hash}39;s what we are asking for," he said, calling for a mandate to pursue offensive operations against troops committing abuses.
The U.N. force is currently mandated to protect U.N. personnel and sites and to protect civilians "under imminent threat of physical violence".
Russia initially blocked an attempt to agree a U.N. Security Council statement endorsing Ouattara as winner this month but finally allowed it to pass as the sheer scale of backing for the ex-IMF official, including from African nations, became evident.
IN HELL, "JUST KEEP GOING"
Local U.N. mission chief Y.J. Choi declined to comment on the mandate but accused Gbagbo&${esc.hash}39;s camp of a media campaign inciting violence against U.N. personnel and said "armed young men" had been sent to harass some staff at their homes.
"However, all these acts will not deter UNOCI from doing its job as we remember one of Winston Churchill&${esc.hash}39;s maxims: &${esc.hash}39;If you are going through hell, just keep going&${esc.hash}39;".
Tensions in Ivory Coast have pushed cocoa futures to four-month highs in recent weeks on market fears of a disruption to supplies <CCc2>. So far, beans have been getting through to port but there have been delays in registering them for export.
UN High Commissioner for Human Rights Navi Pillay cited on Sunday evidence of "massive" violations in Ivory Coast, saying over 50 people had been killed in the previous three days and raising concern over reports of deaths in detention.
She also said hundreds had been abducted from their homes by armed men.
"When people are victims of extrajudicial killings there must be an investigation, and there must be accountability," Pillay said in a statement.
Outside the U.N. headquarters, Ouattara supporters who said they were attacked overnight begged for medical care.
"Masked men attacked us last night," said Salif Kone, 57, a taxi driver who escaped a raid on his Abidjan neighbourhood. "They fired tear gas and bullets. Many were wounded."
Gbagbo&${esc.hash}39;s government has denied using excessive force to put down last week&${esc.hash}39;s protests and says some protesters were armed.
Ouattara&${esc.hash}39;s eight-point poll victory was overturned on grounds of alleged fraud by the Constitutional Council, led by a staunch Gbagbo ally.
Around 5,000 Ivorians have already fled to neighbouring countries as concerns grow that an election designed to draw a line under the 2002-2003 civil war will only harden the division between the rebel-held north and government-controlled south.
Gbagbo retains control over lucrative revenues from both the cocoa and oil sectors, largely based in the south, and his supporters have dismissed international pressure as meddling.
"We have a sole battle: to ensure our dignity, our country&${esc.hash}39;s sovereignty is respected. It is up to us to choose our president," Young Patriots&${esc.hash}39; leader Charles Ble Goude told a rally of the fervently pro-Gbagbo youth movement late on Sunday.
"This battle that we began in 2002 -- we are ready to die for it," said Ble Goude, who was named this month as Gbagbo&${esc.hash}39;s youth minister and who has been on a U.N. sanctions list since 2006 for making public statements advocating violence.
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