WASHINGTON — Biden administration officials have discussed intensifying their sanctions campaign against Russia as evidence emerges of the apparent execution of civilians in a suburb near Kyiv, the Ukrainian capital, according to two people familiar with the matter.

Reports of civilian massacres in Bucha led to swift international condemnation and claims of war crimes from world leaders, as well as pledges to escalate the West’s economic measures against Russia. Ukrainian officials have asked for an investigation by the International Criminal Court into mass graves in Bucha that NATO Secretary General Jens Stoltenberg called “brutality against civilians we haven’t seen in Europe for decades.”

The scope of the potential U.S. retaliatory measures was not exactly clear, but senior Biden officials have previously discussed potentially devastating “secondary sanctions” that would target countries that continue to trade with Russia.

The Biden administration could also impose sanctions on sectors of the Russian economy that it has not hit so far, including mining, transportation and additional areas of the Russian financial sector. The world continues to buy billions of dollars worth of Russian oil and gas, giving the Kremlin a direct financial lifeline. Officials stressed that planning was preliminary and no decisions had been made about potential responses.

Secretary of State Antony Blinken told CNN on Sunday that the United States and its European partners are discussing new sanctions to impose on Russia “every single day.” Blinken stressed that the measures so far are already projected to cause Russia’s economy to contract by 10% this year, but condemned Russia’s “brutality” and said more measures are likely to be necessary.

“These sanctions are having a big bite now. They’re going to have a big bite going forward as long as this lasts, and we are every single day making sure that they’re not only tightened, but increased,” Blinken said.

Blinken added about evidence of Russian war crimes: “There needs to be accountability for it.”

A Treasury Department spokeswoman declined to comment. State Department spokesman Ned Price said: “We’ll continue to escalate the pressure until and unless the Kremlin relents, but we’re not going to preview specific sanctions.”

Bucha’s mayor, Anatoly Fedoruk, told The Washington Post that roughly 270 local residents had been found buried in two mass graves. Roughly three dozen were found dead in the streets, including some who had been bound and executed, Fedoruk told The Post. Bodies of at least 20 men in civilian clothes were found lying on a single street, according to Agence France-Presse journalists.

Some sanctions experts urged the administration to move quickly to respond to these reports.

“This should open the eyes of those in the West that we should push harder on sanctions. There is no excuse to continue funneling billions of dollars to Putin through oil and gas sales,” said Edward Fishman, a former State Department official who worked on Russia sanctions policy during the Obama administration. “I’m confident we will end up with maximalist 10 out of 10, Iran-style sanctions on Russia. Events like this galvanize the West to do so. … I don’t see any rationale in waiting.”

Many European officials have openly began calling for new sanctions to be imposed as soon as Wednesday. Both Germany and France’s foreign ministers have already vowed to push for strengthened sanctions, citing the atrocities in Bucha, according to the Financial Times.

“We need a 5th round of strong E.U. sanctions as soon as possible,” said Kaja Kallas, Estonia’s prime minister, on Twitter.

The Ukrainian government has for weeks been urging the White House to expand its sanctions campaign to more dramatically cut Russia off from the global economy. Ukraine has pressed the administration to curb Russian vessels’ access to international waterways, to choke off its energy exports and to sanction far more government officials and allies of Russian President Vladimir Putin. Europe continues to depend on Russian energy, and cutting off that vital financial lifeline could devastate European economies.

It is not clear what escalatory matters would be proportional to the atrocities emerging in Ukraine. Richard Nephew, a senior research scholar at Columbia University, said it has been long understood that human rights violations would trigger more sanctions. But he pointed out that Russian military tactics do not appear to be driven by U.S. sanctions, and it would be hard to design new measures commensurate with the damage done.

“The real problem they’re going to have with the sanctions response is it will be seen as insufficient pretty much no matter what you do. The humanitarian atrocity committed will always be much worse than a sanctions response,” Nephew said. “There’s nothing proportional to a massacre being committed.”