HORLIVKA, Ukraine — Ukraine's acting President Oleksandr Turchynov today called for the deployment of United Nations peacekeeping troops in the east of the country, where pro-Russian insurgents have occupied buildings in nearly 10 cities.

In a telephone conversation with Secretary-General Ban Ki Moon, Turchynov suggested an “anti-terrorist operation” could be conducted jointly by Ukrainian security forces and U.N. peacekeepers, according to the presidential website.

Peacekeepers would have to be authorized by the U.N. Security Council, in which Russia holds a veto.

The request comes from a government that has proved powerless to reign in separatists in the Russian-speaking east of the country, where insurgents have been occupying government offices in cities for the past week. A deadline for the insurgents to give up weapons and vacate the brigands, set by Turchynov, passed this morning without any visible action.

PERTH, Australia — Search crews sent a robotic submarine deep into the Indian Ocean for the first time today to begin scouring the seabed for the missing Malaysian airliner after no signals from its black boxes were detected for six days.Meanwhile, officials were investigating an oil slick about 3.4 miles from the area where the last underwater sounds were detected, said Angus Houston, the head of a joint agency coordinating the search off Australia’s west coast.Crews have collected an oil sample and are sending it back to Australia for analysis, a process that will take several days. Houston said it does not appear to be from any of the ships in the area, but cautioned against jumping to conclusions about its source.The unmanned underwater vehicle, the Bluefin 21, was launched from the Australian navy ship Ocean Shield, the U.S. Navy said. The autonomous sub can create a three-dimensional sonar map of any debris on the ocean floor.