Ukraine's President Petro Poroshenko says he will "calm" fighting between his forces and Russian-backed separatists in the country's east a day after rocket fire killed 30 people in and around the port city of Mariupol.
Poroshenko, speaking after an emergency meeting of Ukraine's security council, said reviving a shattered peace deal agreed in September was the only way out of the conflict.
The Ukrainian leader also said that, in case there was any doubt, intercepted radio transmissions showed conclusively that it was the rebels who attacked government-held Mariupol, hitting an open-air market and a residential area.
The Associated Press notes that "the attack on Mariupol, a strategically situated port city that had been relatively quiet for months, alarmed the West and looked likely further to aggravate relations with Russia."
President Obama, speaking in New Delhi, said the U.S. was prepared to "ratchet up the pressure on Russia" to get it to stop supporting the separatists.
"We are deeply concerned about the latest break in the ceasefire and the aggression that these separatists — with Russian backing, Russian equipment, Russian financing, Russian training and Russian troops — are conducting," Obama told a news conference in India.
"I will look at all additional options that are available to us short of military confrontation and try to address this issue. And we will be in close consultation with our international partners, particularly European partners," he said.
"More than 5,000 people have been killed in fighting since the rebels seized a large swathe of Donetsk and Luhansk regions last April, UN officials say. More than a million people have been displaced.
"Ukraine and the West have accused Russia of arming the rebels and sending its troops into Ukrainian territory.
"Russia has denied directly arming the separatists, and blames Ukraine for the upsurge in fighting."