A Mexican businesswoman who headed a group of 600 families searching for their disappeared relatives has been killed.

Miriam Rodríguez Martínez was shot in her home in the town of San Fernando in Tamaulipas state.

She was known for successfully investigating the kidnap and murder of her daughter by a local drug cartel, the Zetas.

The information she gave the police ensured the gang members were jailed.

But in March one of them escaped and her colleagues said she started to receive threats.

She was killed on Mexico's mother's day, 10 May.

Her colleagues said she had asked for police protection but was ignored.

State prosecutor Irving Barrios told a news conference that security needs had been met and police officers made rounds three times a day. Her family disputes this.

The Mexican human rights commission issued a statement saying it deplored her murder and called for a full investigation.

The UN in Mexico tweeted its condemnation of the murder

Mrs Rodríguez founded the local group for families who were victims of violence after her daughter, Karen Alejandra, was kidnapped in 2012.

She had managed to find her daughter's body in a clandestine grave and put her murderers in jail.

She also foiled an attempted kidnapping by the Zetas of her husband, when she chased the gang in her car, at the same time notifying the army who then managed to arrest them.

According to one of her fellow campaigners, Mrs Rodríguez felt she could not sit back after her daughter's killers were caught.