WASHINGTON — Computer systems used by Hillary Clinton’s presidential campaign were hacked in an attack that appears to have come from Russia’s intelligence services, a federal law enforcement official said on Friday.

The apparent breach, coming after the disclosure last month that the Democratic National Committee’s computer system had been compromised, escalates an international episode in which Clinton campaign officials have suggested that Russia might be trying to sway the outcome of the election.

Mrs. Clinton’s campaign said in a statement that intruders had gained access to an analytics program used by the campaign and maintained by the national committee, but it said that it did not believe that the campaign’s own internal computer systems had been compromised.

The Democratic Congressional Campaign Committee, the fund-raising arm for House Democrats, also said on Friday that its systems had been hacked. Together, the databases of the national committee and the House organization contain some of the party’s most sensitive communications and voter and financial data.