• About half of states are expected to introduce new restrictions or bans after the court overturned its 50-year-old Roe v Wade decision.
• In Los Angeles protesters briefly blocked traffic on a highway.
Clinics have begun closing in some US states after a Supreme Court ruling on Friday removed American women's constitutional right to abortion.
About half of states are expected to introduce new restrictions or bans after the court overturned its 50-year-old Roe v Wade decision. Of these 13 have outlawed abortion instantly.
President Joe Biden described the ruling as "a tragic error".
Protests are under way in cities across the US.
In Phoenix, Arizona, police fired tear gas after pro-choice protesters banged on the doors and windows of the state capitol. In Los Angeles protesters briefly blocked traffic on a highway.
At an abortion clinic in Little Rock, Arkansas - a state with a so-called trigger law allowing an instant ban - the doors to the patient area shut as soon as the court's opinion was posted online and sobbing could be heard. Staff made calls to tell women that their appointments were cancelled.
"No matter how hard we prepare for bad news, when it finally hits, it hits hard. Having to call these patients and tell them Roe v Wade was overturned is heartbreaking," nurse Ashli Hunt told the BBC.
Escorts at the clinic, who stood in the Arkansas heat day in and day out to accompany patients through the throng of protesters, held a group hug. "I thought that this country would still care about people. Would still care about women," said Miss Karen, the lead escort.
Outside, anti-abortion protesters celebrated.
"You are on notice!" shouted a protester at people still parking their cars at the clinic who had not heard about the decision yet. "My suggestion is for you turn around and leave this place of sin, this place of inequity, this evil place."
In New Orleans, Louisiana - another trigger law state - the Women's Health Care Centre, one of only three abortion providers in the state, was closed and its staff had gone home.
Outside the clinic, volunteer escort Linda Kocher told the BBC that rich women would still be able to access abortions in other states but "poor women will end up in a back alley" for illegal procedures. But anti-abortion campaigner Pastor Bill Shanks said it was a "day for celebration".
Overall, the Supreme Court ruling is expected to mean about 36 million women of reproductive age will lose access to abortion in their states, according to research from Planned Parenthood, a healthcare organisation that provides abortions.
- Trigger laws in Kentucky, Louisiana, Arkansas, South Dakota, Missouri, Oklahoma and Alabama have already been applied
- Bans in Mississippi and North Dakota will come into effect after their attorney generals approve it
- Wyoming's ban will take effect in five days, Utah's ban must be certified by a legislative council
- Bans in Idaho, Tennessee and Texas will be applied in 30 days.
The decision was met with elation by anti-abortion campaigners outside the court in Washington, but protests against the ruling were due to be held in more than 50 cities across the US.
Although a divisive issue in the US, a recent Pew survey found that 61% of adults say abortion should be legal all or most of the time, while 37% say it should be illegal all or most of the time.
In San Antonio, Texas, anti-abortion advocate Tere Harding said she was working on a security plan in case protests targeted the crisis pregnancy centre she runs on the outskirts of the city.
"Every human life needs to be protected," she told the BBC as she watched Mr Biden criticise the Supreme Court decision. "It represents that we acknowledge the humanity of the unborn."
Mr Biden said the ruling put women's health and lives at risk.
"It's a realisation of an extreme ideology and a tragic error by the Supreme Court," he said.
He said he would work to ensure that state and local officials could not prevent women travelling to have abortions in states where the procedure is legal, and would also protect women's access to contraception and medication to end pregnancies of up to 10 weeks that is used to treat miscarriages.
Friday's ruling amounts to a wholesale reversal of the Supreme Court's own legal precedent - an extremely rare move - and is likely to set up political battles that divide the nation.
The governors of west coast states California, Washington and Oregon have vowed to protect patients travelling from other states for an abortion.
In states where opinions on abortion are closely split - such as Pennsylvania, Michigan and Wisconsin - the legality of the procedure could be determined on an election-by-election basis. In others, the ruling may set off a new round of legal battles, including over whether individuals can go out of state for abortions or order abortion drugs through mail services.
Meanwhile former Vice-President Mike Pence, a long-standing critic of Roe v Wade, urged anti-abortion campaigners not to stop until "the sanctity of life" was protected by law in every state.
How the decision was made
The landmark 1973 Roe v Wade case saw the Supreme Court rule by a vote of seven to two that a woman's right to terminate her pregnancy was protected by the US constitution.
The ruling gave American women an absolute right to an abortion in the first three months (trimester) of pregnancy, but allowed for restrictions in the second trimester and for prohibitions in the third.
But in the decades since, anti-abortion rulings have gradually pared back access in more than a dozen states.
In its current session, the Supreme Court had been considering a case, Dobbs v Jackson Women's Health Organization, that challenged Mississippi's ban on abortion after 15 weeks.
By ruling in favour of the state, the conservative-majority court effectively ended the constitutional right to an abortion.
Five justices were firmly in favour: Samuel Alito, Clarence Thomas, Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett.
Chief Justice John Roberts wrote a separate opinion saying that, whilst he supported the Mississippi ban, he would not have gone further.
The three justices who disagreed with the majority - Stephen Breyer, Sonia Sotomayor and Elena Kagan - wrote that they had done so "with sorrow - for this court, but more, for the many millions of American women who have today lost a fundamental constitutional protection".
The reversal of a long-standing precedent has also raised fears for other rights decided upon by the Supreme Court in the past.
Justice Clarence Thomas, in his opinion, wrote: "In future cases, we should reconsider all of this Court's substantive due process precedents, including Griswold, Lawrence, and Obergefell" - referencing three landmark decisions of the past on the right to contraception, the repeal of anti-sodomy laws, and the legalisation of same-sex marriage respectively.