Secretary of State John Kerry called Russian Foreign Minister Sergey Lavrov Tuesday afternoon to express his “deep concern” after a deal aimed at reducing violence in Ukraine has resulted in little movement from pro-Russian separatists.

“The secretary expressed deep concern over the lack of positive Russian steps to de-escalate, and cited mounting evidence that separatists continue to increase the number of buildings under occupation, and take journalists and other civilians captive,” a senior State Department official said.

{mosads}The official said Kerry urged Russia “to tone down escalatory rhetoric” and issue public statements “calling for those occupying buildings to disarm and stand down in exchange for amnesty.” The U.S. says Russia agreed to those terms in a multilateral deal reached in Geneva last week.

“Secretary Kerry also reiterated that the absence of measurable progress on implementing the Geneva agreement will result in increased sanctions on Russia,” the official said.

The call came as Ukraine’s acting president urged law enforcement agencies to renew their crackdown against separatist forces within Ukraine. He accused pro-Russian rebels of torturing and killing two people near the city of Slaviansk, including Vladimir Rybak, a local politician who belonged to the president’s party.

“The terrorists who basically have taken the entire Donetsk region hostage have crossed the line with torturing and killing Ukrainian patriots,” interim President Oleksandr Turchynov said, according to CNN.

Earlier Tuesday, Vice President Biden called on Russia to “stop supporting men hiding behind masks and unmarked uniforms sowing unrest in eastern Ukraine” during his visit to Kiev.

The vice president warned that more “provocative behavior” would be met with additional sanctions from the U.S., and he announced a new aid package aimed at stabilizing the Ukrainian economy and assisting with next month’s presidential elections.

“You will not walk this road alone. We will walk it with you,” Biden said.

White House press secretary Jay Carney wouldn’t outline a concrete timeline for when the U.S. might move ahead with a broader sanctions regime.

“I think Russia understands that the United States, the E.U. and our G-7 partners are serious about the need for all parties to the agreement to take steps to de-escalate the situation in Ukraine and that, should Russia continue to engage in provocative actions, continue to support the separatists — the so-called separatists, or the armed irregular militias in portions of Ukraine who have seized buildings — that there will be further costs imposed on Russia,” Carney told reporters aboard Air Force One.

Kerry also spoke by phone with Ukrainian Prime Minister Arseniy Yatsenyuk, who met with Biden earlier in the day. According to the State Department, Kerry praised Yatsenyuk for proceeding with amnesty legislation that would wipe away criminal charges for militants who agree to leave buildings they’ve seized in the country’s eastern region. Kerry also thanked Yatsenyuk for his efforts on a national constitutional reform “dialogue,” according to the administration official.

“Secretary Kerry encouraged final passage of the amnesty legislation and the formal launch of the national dialogue, including the issuance of invitations to a broad range of participants,” the official said.