More than 20 people have been injured in clashes between migrants and police in the town of Tapachula, on Mexico's southern border, officials say.

Mexico's National Migration Institute (INM) said about 100 migrants, mainly from Cuba, Haiti and countries in Africa, joined in "violent protests".

The INM said the migrants were trying to jump the queue for permits to allow them to continue their journey north.

Every year, hundreds of thousands of people cross Mexico headed to the US.

Migrants threw stones and sticks at members of the National Guard and scuffles broke out between the two sides.

Rights activist Irineo Mujica told Reuters news agency that the migrants were "desperate" after waiting for months to be given an appointment with Mexico's immigration authorities.

Most have been sleeping rough by the roadside and are relying on handouts to feed themselves.

While many want to reach the United States and are waiting for papers that will allow them to cross the country without being detained, others are applying for refugee or asylum status to be able to stay in Mexico.

Official data suggests that the number of people requesting refuge or asylum in Mexico almost doubled between 2019 and 2021, overwhelming the authorities.

The immigration centre in Tapachula - the biggest in Mexico - has become one of the main bottlenecks on migrants' journeys and the United Nations refugee agency has urged the authorities to do more to clear the backlog.

Last week, a group of migrants in the town sewed their mouths shut in protest at the slow pace at which their requests are being processed.