U.N. envoy to Yemen Martin Griffiths is seen during his departure at Sanaa airport, Yemen November 24, 2018. REUTERS/Mohamed al-Sayaghi?

DUBAI (Reuters) - U.N. special envoy Martin Griffiths arrived in Sanaa on Monday to escort Houthi negotiators to Sweden, where they are due to take part in U.N.-sponsored peace talks, a Reuters TV reporter said.