ISLAMABAD (AP) — A Pakistani mountaineering official says a Polish K2 expedition has expressed concern after a member abandoned the team following a dispute with fellow climbers to attempt a solo ascent of the world's second-highest peak in winter.

Karrar Haidri of the Alpine Club of Pakistan said Monday that Denis Urubko's attempt to climb the summit alone is highly risky.

Expedition spokesman Michal Leksinski tweeted they had no radio communication with Urubko, who left base camp on Sunday without informing the expedition management.

Urubko was part of last month's mission, along with Adam Bielecki, that rescued French mountain climber Elisabeth Revol from Nanga Parbat, another Himalayan peak in Pakistan. Her climbing partner was injured and is presumed to have died during that summit.

Bielecki tweeted he was worried for the "lone climber."