LONDON — British Prime Minister Theresa May has met with the mother of detained Venezuelan opposition leader Leopoldo Lopez and says she is “deeply troubled” by the jailing of political prisoners in the country.

May met Thursday at 10 Downing St. with Antonieta Lopez and with Julio Borges, president of the Venezuelan National Assembly.

Lopez is under house arrest after being released from a jail sentence for leading anti-government demonstrations. May said his detention was “a matter of great concern.”

May urged President Nicolas Maduro’s government to “ensure that human rights, the rule of law, the separation of powers and the integrity of democratic institutions are respected.”

She expressed “unwavering support for the National Assembly as a democratic institution.” The Maduro government stripped the elected assembly of its powers earlier this year.