A new law increasing the legal age of marriage to 18 has come into force in England and Wales.
Previously people could get married at 16 or 17 if they had parental consent and there was no law against ceremonies for younger children which were not registered with local councils.
The new legislation also covers non-legally binding ceremonies.
The government said the changes would help protect vulnerable children from being forced into marriage.
Previously forced marriage was only an offence if coercion, such as threats, was used.
But under the Marriage and Civil Partnership (Minimum Age) Act, it is now illegal to arrange for children to marry under any circumstances, whether or not force is used.
Those found guilty of the offence face up to seven years in prison.
The changes do not apply in Scotland and Northern Ireland, where the minimum age for marriage will remain 16. In Northern Ireland parental consent is required for those under 18 but not in Scotland.
Ministers in Northern Ireland have previously said they plan to increase the minimum age of marriage to 18 but with the devolved government not currently functioning legislation cannot be brought forward.
Campaigner Payzee Mahmod is a survivor of child marriage and her sister Banaz was murdered in a so-called honour killing after leaving her husband, who she was forced to marry at the age of 17.
She said seeing the new law come into force in England and Wales was “probably one of the most important days of my life”.
“It’s very emotional for me because I know truly, in great detail, the harms of child marriage,” she told media.
“I’ve personally been through it, I’ve seen my sister go through it. And I’ve seen the devastating impacts that it can have for so many women and girls.
“When they try to leave child marriages, the ultimate penalty is death and this is exactly what happened in my sister’s case.”
Payzee said the changes would mean “the onus is no longer on the child to have to speak up against their parents or their community when they are faced with child marriage”.
In 2021 the government’s Forced Marriage Unit provided support in 118 cases involving victims who were under 18.
However, campaigners believe official figures do not reflect the true scale of the problem as other victims may not have been able to reach out for support.
The charity Karma Nirvana, which supports victims of forced marriage, hopes the new law will help increase identification and reporting of child marriage.
Director Natasha Rattu said it was “a huge leap forward to tackling this usually hidden abuse and will provide a greater degree of protection to those at risk”.
Justice Secretary Dominic Raab said: “Those who act to manipulate children into marrying under-age will now rightly face the full force of the law.”
However, Mihai Bica, from the Roma Support Group, said he was concerned about how the changes would be communicated to communities and those enforcing the new law.
He explained that in Roma communities the word “married” could be used to describe a boyfriend-girlfriend relationship and “cultural misunderstanding” might result in “serious implications for families who should not be subject to this law”.
Mr Bica called for training of staff so they were not “influenced by the existing stereotypes” when assessing Roma families.
The changes, which had cross-party support, were introduced through a bill brought to Parliament by Conservative MP Pauline Latham.
Pope Francis, who often defends the rights of migrants, has said he is praying for the dead, the missing and those who survived.
According to monitoring groups, more than 20,000 people have died or gone missing at sea in the central Mediterranean since 2014.
Regina Catrambone, director of the Migrant Offshore Aid Station, which carries out search and rescue operations in the Mediterranean, told the media that European countries must work together to help those in need.
She also called for an end to the “myopic vision” that says that countries that are physically closer to Africa and the Middle East should take the lead on tackling the issue.
“Still there is no co-operation among the European states to actively co-ordinate together to go and help the people in need,” she said, urging governments to work together to improve search and rescue efforts and develop safe and legal routes.