US House of Representatives Speaker Nancy Pelosi's husband Paul Pelosi was assaulted during a break-in at the couple's San Francisco home early on Friday and a suspect has been arrested, authorities said.
Paul Pelosi, 82, was taken to hospital and is expected to make a full recovery, Pelosi's office said.
The Democratic speaker, who is second in the succession line of the US presidency, was in Washington with her protective detail at the time of the assault, according to the US Capitol Police.
The Capitol Police said a motive for the attack was still under investigation.
CNN, citing a source, reported that the assailant shouted "Where is Nancy?" before the attack. The Associated Press reported the hammer-wielding assailant specifically targeted the Pelosis' home.
It was unclear how the intruder got into the three-story red brick townhouse in the affluent Pacific Heights neighbourhood. Aerial photos showed shattered glass on a door at the rear of the house. Streets around the residence were closed off on Friday morning.
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The assault occurred less than two weeks before the Nov. 8 midterm elections, in which control of the House and US Senate is at stake.
San Francisco police said they responded to a home break-in at 02:27 a.m. Pacific time (0927 GMT) and took a suspect into custody. Further details were expected at a news conference scheduled for 09:30 a.m Pacific Time (1630 GMT).
Paul Pelosi was being treated for bruising, severe swelling and other injuries after being severely beaten in the head and body by an assailant wielding a hammer, the Associated Press reported, citing two sources with knowledge of the investigation.
President Joe Biden called Pelosi on Friday morning to express his support, according to White House spokesperson Karine Jean-Pierre.
House Republican Leader Kevin McCarthy also said he reached out to Pelosi, while Senate Republican Leader Mitch McConnell said he was "horrified and disgusted" by the attack.
The Capitol Police, responsible for protecting Congress, said it was working with the FBI and San Francisco police on the investigation.
New York City police warned on Thursday that extremists could target politicians, political events and polling sites ahead of the midterm elections.
Republicans have been campaigning on concerns about violent crime, as well as inflation and other quality-of-life issues. San Francisco's crime rate in 2021 was 1.5 times the national average, according to several crime-tracking websites.
As a Democratic leader in Washington and a longtime representative from one of America's most liberal cities, Pelosi, 82, is a frequent target of Republican criticism and is often featured in attack ads.
Her office was ransacked during the Jan. 6, 2021, attack on the US Capitol by supporters of Republican then-President Donald Trump, some of whom hunted for her during the assault.
In January 2021, her home was vandalised with graffiti saying ""Cancel rent" and "We want everything" painted on the house and a pig's head left in front of the garage, according to media reports.
McConnell's home also was vandalised around that time.
In a politically polarised climate, threats against Republican and Democratic lawmakers have been on the rise. Capitol Police said they investigated 9,625 incidents in 2021, nearly a threefold increase from 2017.
A gunman angered by Trump shot and wounded five Republican members of Congress at a baseball practice in 2017, and Democrat Gabby Giffords was shot in the head at a public appearance in 2011.
Paul Pelosi, who owns a San Francisco-based real estate and venture capital firm, was convicted of a misdemeanour charge of driving under the influence of alcohol after becoming involved in an auto accident in May. He was sentenced to five days in jail in Napa County, California.