Geneva: Top US diplomat John Kerry arrived in Switzerland late Sunday for tough talks on Iran and Ukraine, and to push Moscow`s foreign minister to ensure a "credible" investigation into the killing of opposition leader Boris Nemtsov.
Less than a week after accusing Russian officials of lying `to my face" about the fighting in eastern Ukraine, Kerry will have likely tense discussions with Russian counterpart Sergei Lavrov.
He will also step up the pace of nuclear talks with Iran`s top diplomat Mohammad Javad Zarif with a series of meetings planned over the next three days.
Earlier Sunday Kerry urged Russia to carry out a "thorough, transparent, real investigation" into the murder of Nemtsov, a Russian opposition leader who fiercely criticized President Vladimir Putin.
Nemtsov was shot dead in Moscow on Friday, just two days before he was due to lead a major anti-government rally.
From Switzerland, Kerry is expected to travel to Saudi Arabia to meet with King Salman before flying to London to join a conference of foreign ministers from the Gulf Cooperation Council.
