Gunmen armed with machine guns stormed the foreign ministry of Libya's internationally recognized government in Tripoli on Tuesday, killing three people who worked there, a spokesperson for the UN-backed Government of National Accord told CNN.

One of the victims was a high-ranking official, the spokesperson added. 10 others were injured, according to the Health Ministry.

Three gunmen died in the attack that happened at around 10 a.m. local time. One of the gunmen is believed to have been killed after an explosion was heard in the top floor of the building, politician Guma El-Gamaty who was in the area said.

"The top floor was totally engulfed in fire; you can still see smoke coming from the building," he said.

Gamaty added that emergency services and security forces were on the ground dealing with the situation, which he believed was under control.

The United Nations Support Mission in Libya condemned the attack.

"Terrorism will not triumph over the Libyans' decision to move forward towards building their state and renouncing violence. We will not accept any attack on a state institution, especially one committed by a terrorist group," said Ghassan Salamé, the Special Representative of the Secretary-General in Libya.

"We will work with the Libyan people to prevent terrorist groups from turning Libya into a haven or an arena for their crimes."