Haile Menkerios met Guinea's military ruler in Conakry
A senior UN official has started his investigation into the killing of opposition demonstrators in Guinea.
UN Assistant Secretary General Haile Menkerios is to investigate the events of 28 September, when Guinean soldiers opened fire on the protesters.
They were calling on Guinea's military ruler not to stand for election.
A BBC correspondent says Mr Menkerios' arrival is the most powerful sign yet that the world beyond Africa intends to pursue the case.
Human rights groups say some 157 people died in last month's clashes, but the junta puts the toll at 57.
On Sunday, Mr Menkerios met the military ruler, Capt Moussa Dadis Camara, Guinean Prime Minister Kabine Komara, and members of the opposition.
"The prime minister assured me that the government welcomes the investigation and will co-operate with it," Mr Menkerios said, reports the AFP news agency.
The Guinean authorities have blamed the September killings on out-of-control soldiers and opposition provocation.
Capt Camara has himself called for an investigation.
BBC West Africa correspondent Caspar Leighton says the arrival of the UN team in Conakry adds to the broad international pressure being put on the military government to write itself out of Guinea's political future.
So far Capt Camara has yet to yield, despite Saturday's African Union deadline for him to do so.
"Legally speaking, the deadline has expired but politically, we are still working to put pressure on the junta. It's the result that matters most," said AU Peace and Security Commissioner Ramtane Lamamra.
Capt Camara seized power in December 2008 and initially said he would not stand in the elections he announced for January 2010.
His coup after years of authoritarian rule under Lansana Conte was initially popular.
But rumours that he would seek election led to massive street protests, culminating in last month's bloody crackdown.