Most ministers at an EU meeting in the Latvian capital said Europe should only consider tightening sanctions if the ceasefire was seriously violated.
Two men have been detained over the Russian opposition figure's slaying, according to the head of the country's Federal Security Service.
Ukrainian authorities will ensure “all necessary measures are taken to protect the life and health” of the woman, prosecutors said.
The EU's foreign minister, Federica Mogherini, said there could be a fourth round of Russian sanctions if fighting persists.
Boris Nemtsov had criticized Putin in a radio interview hours before he was murdered in Moscow last Friday.
Reports from border-crossing points between Ukraine and Russia say more are returning than leaving since February's ceasefire.
Parliament has voted to expand the nation's troop level to 250,000, as heavy weapons withdraw on the front lines.
At least 32 miners were killed after an explosion in a coal mine in rebel-held territory on Tuesday.
The head of Russia’s Security Council accused the U.S. of funding Russian opposition groups.
Days ahead of the first anniversary of the aircraft's mysterious disappearance, Tony Abbott hinted that the search may be scaled back.
In a speech before the Security Council, the Libyan ambassador said the world has not done enough to stop the spread of terrorism.
Boris Nemtsov's allies have pledged to publish a report he was working on at the time of his death.
The U.S. military will arrive in Romania and Bulgaria before expanding operations to other regions of Eastern Europe.
At least 17 deaths at a Ukraine coal mine Wednesday bring the 15-year death toll there to more than 300.
Many opposition members and Kremlin critics accuse the Russian president's inner circle of orchestrating Boris Nemtsov's murder.
Graham indicated interest in a run for president in January, but South Carolina voters say he should skip 2016.
A miner, Sergei Baldayev, said five bodies had been retrieved from the area of the blast, in a shaft deep underground.
Before his death, Boris Nemtsov, a vocal critic of Putin, had been organizing an upcoming rally in protest of the conflict in eastern Ukraine.
Army Gen. Martin Dempsey said the U.S. should consider giving “lethal aid” to Ukraine in its fight against pro-Russian separatists.
White House spokesman Josh Earnest said Obama condemned Russia for not following through on its agreements in a video conference call with European leaders.
Ukraine says rebels violated the ceasefire six times between Monday and Tuesday.
The economic crisis has been particularly felt in Donetsk, where goods are scarce and prices have soared.