New York, Jan 14 (DPA) UN Secretary General Ban Ki-moon described quake-stricken Haiti as 'grim' Thursday as rescuers worked frantically to save people buried under rubble, and at least 150 members of the UN mission staff there remained missing.

Ban Ki-moon said at UN headquarters in New York that conditions in Port-au-Prince remain unchanged.

At least 22 UN staffers housed at the Christopher Hotel in the Haitian capital were known to have died at the latest count, he said.

The UN said 150 members of the mission remained unaccounted for Thursday, up from an earlier estimate of 100.

He said overall available information was still sketchy and the UN could only make educated guess about the casualties.

'I fear it could be very high,' Ban said, adding that the next 24 hours are critical to rescue efforts as more time passes since the magnitude 7 quake Tuesday.