A forest ranger has been killed in Virunga national park in the Democratic Republic of the Congo, weeks after the reserve was reopened to tourists.

Virunga, home to critically endangered mountain gorillas as well as hundreds of other rare species, was shut for more than eight months for a review of security after a series of attacks on staff last year.

A statement from the park said the ranger, Freddy Mahamba Muliro, died during an attack on a ranger position in its central sector. It gave no further details.

“We are in deep mourning for Ranger Freddy. It is a tragedy that his young life has been cut short in dedicated service to Virunga. Now more than ever, Ranger Freddy’s death highlights the very real threats to our rangers in their protection of Virunga national park,” said Emmanuel de Merode, the park’s director. More than 170 rangers have been killed in Virunga in recent decades. At least 12 died in clashes with militia and smugglers in Virunga in the months before the closure, one of the bloodiest periods in the park’s history.

In May one of the many local militias, Mai Mai, attacked a vehicle carrying tourists from the city of Goma, about 30 miles from the park headquarters, to their accommodation. A 25-year-old ranger was shot dead, a Congolese driver was wounded and two British tourists, Robert Jesty and Bethan Davies, were held by the militia overnight.

Following that attack, De Merode, a Belgian aristocrat, said the decision had been taken reluctantly to close Virunga to tourists to allow a thorough review of security precautions and reinforcement of the 700 rangers deployed to keep animals and visitors safe.

The park, located in the DRC’s North Kivu province, has a reputation as one of the most dangerous conservation projects in the world. It faces multiple security threats including illegal charcoal production, smuggling and poaching, as well as from the Mai Mai militia. Health authorities and NGOs have struggled to contain an Ebola outbreak.

Violence in the region has been aggravated by continuing political instability. Presidential elections were held last year, and the long-time ruler Joseph Kabila stepped down after the opposition leader Felix Tshisekedi was declared the winner.

Virunga, founded in 1925 by Belgian colonial authorities, struggled in the immediate aftermath of the country’s independence in 1960 but flourished under President Mobutu Sese Seko, a flamboyant and wasteful authoritarian ruler who took power in 1965.

The park suffered during the civil war that followed Mobutu’s chaotic fall in 1997. Virunga’s mountain gorilla population sank to 300. It now stands at more than 1,000, while the numbers of other animals such as forest elephants are also rising.

In 2007 a partnership was established between charities funded by private donors, the European Union and the Congolese wildlife service. De Merode took charge and implemented wide-ranging reforms.

The rangers, who are recruited from nearby villages, are paid a monthly salary of $250, a sizeable sum locally. Initiatives have focused on local communities, with micro-loans and hydroelectric power projects to boost the local economy.