After a much-criticized delay, President Barack Obama visited flood-stricken Louisiana Tuesday, defending his administration's response and urging citizens to pitch in and help ravaged communities.

Obama -- decked out in hiking boots and with shirt sleeves rolled up -- touched down in Baton Rouge and toured a hard-hit and debris-strewn parish, promising Louisianans they would get all the help they need.

At least 13 people have died and more than 100,000 people have registered for US government emergency assistance as a result of the flooding.

The National Guard has been deployed and the federal government has approved more than $120 million in assistance for temporary rent, home repairs and flood insurance payments.

"I am asking every American to do what you can to help get families and local businesses back on their feet," Obama said, directing people to the website volunteerlouisiana.gov and aid groups like the Red Cross.

"These are some good people down here," he said. "They shouldn't have to do it alone."

Obama has been lampooned for not cutting short a two-week vacation on Martha's Vineyard to visit the Gulf Coast state.

Heavy rains began on August 11 and quickly submerged thousands of homes.

In just a few days, 31 inches (79 centimeters) of rain fell on some parts of the low-laying state -- where the highest point is just 535 feet (165 meters) above sea level.

The disaster brought back painful memories of Hurricane Katrina, which 11 years ago inundated nearby New Orleans and brought searing criticism of the federal government's response.

Images of president George W. Bush looking out the window of Air Force One as he flew over New Orleans became emblematic of perceived government detachment from the crisis.

As a presidential candidate, Obama was quick to criticize the "unconscionable ineptitude" of the Bush administration.

- Political football -

A few months out from November's election, Obama's visits have inevitably become another talking point on the campaign trail.

Republican presidential nominee Donald Trump visited Louisiana last week, and goaded the golf-loving president about his absence.

"Honestly, Obama ought to get off the golf course and get down there," Trump said.

Obama dismissed such criticism, saying: "This is not a photo-op issue."

"This is (about) how do you make sure that a month from now, three months from now, six months from now, people still are getting the help that they need," he added.

"One of the benefits of being five months short of leaving here is I don't worry too much about politics."

Louisiana's Democratic Governor John Bel Edwards -- who had warned Trump not to turn his visit into a photo op and called for him to make a donation -- also asked Obama for more help.

In a letter to Obama, he called for several funding mechanisms to be activated and for a recovery task force to be established.

Democratic nominee Hillary Clinton has said she will visit the state later, in an implicit criticism of Trump.

"I am committed to visiting communities affected by these floods, at a time when the presence of a political campaign will not disrupt the response," she said, while calling for donations to the Red Cross.

Republicans usually win the state of Louisiana handily in presidential elections.

The last Democratic presidential nominee to win there was Clinton's husband, former president Bill Clinton, in his 1996 rout of Bob Dole.

Before leaving Baton Rouge, the White House said Obama met the family of Alton Sterling, a black man whose shooting by a white police officer triggered protests and a Justice Department investigation.

The president also met with the families of dead and injured officers.