Houthi security forces have detained at least 15 Yemeni employees of international organizations including the United Nations, three officials of Yemen's internationally recognized government told Reuters on Friday.

In a series of raids on Thursday, armed Houthi intelligence officers detained nine UN employees, three employees of the US-funded pro-democracy group National Democratic Institute (NDI) and three employees of a local human rights group, the officials said.

Intelligence officers of the Houthi group, which controls the capital Sanaa and large parts of the north of the country, raided the homes and offices of these people, confiscating phones and computers.

The detained UN employees work for the human rights office and the office for humanitarian affairs, said the officials, from the internationally recognized government that controls mostly southern parts of Yemen.

The Houthis are closely aligned with the Islamic Republic of Iran, which has a long history of detaining foreign nationals, often charging them with espionage, and using them as bargaining chips against Western governments.

Neither the UN office nor NDI immediately responded to a Reuters request for confirmation or comment. A Houthi spokesperson did not immediately comment.

The Houthis, who are aligned to Iran and have attacked shipping in the Red Sea drawing air strikes from the United States and Britain, have held around 20 Yemeni employees of the US embassy in Sanaa for the past three years. The embassy suspended operations in 2014.

Reporting by Reuters