Three elderly nuns have been tied up, gagged and assaulted in a village in Mexico, nine months after the parish priest in the same village was subject to a similar attack.

The priest, who was severely beaten about the head in the attack on him last September, had recovered and was back at work in the parish when the nuns were held hostage for hours and also badly beaten up.

The three nuns, from the Sacred Heart convent in the Matias Romero municipality in Oaxaca State, were also robbed as was the priest.

The Bishop of Tehuantepec, Oscar Campos Contreras, accused the authorities of failing to do enough to stop the attacks.

He said: "We observe with sadness and indignation that this violence has not been combatted in a timely or effective manner. Indifference, under-handedness, and on occasion the complicity of public institutions and society itself have tolerated and fostered the growth of criminality."

"We cannot continue to avoid our responsibility to eradicate this evil that will end by destroying social development and even the lives of many people, including the lives of our young people. For this reason as citizens and as believers we take a stand against all kinds of violence.

"We ask the Authorities, who are responsible for protecting the security of citizens, that they do their job to eradicate this social evil which appears to be expanding like a plague in our region."

In 2014, according to the Vatican, more Catholic priests were killed in Mexico than anywhere in the world.

Father Omar of the Catholic Multimedia Centre told Christian Solidarity Worldwide that police can be quick to label attacks on priests as "common crime", even when the attack is accompanied by vandalism or desecration of the church, and that full investigations are rare

He highlighted the impact of these types of attacks on religious freedom, including priests under threat having to leave their parish and in some cases, closure of a parish.

Mervyn Thomas, chief executive of CSW, said: "The situation is very complex and all of Mexican society, including communities of faith, is affected by the culture of impunity. We remain deeply concerned by the impact of the violence, and in particular impunity, on freedom of religion or belief, and we stand in solidarity with religious leaders like Father López Nolasco, who continue to carry out their ministry despite the very real risks."