Often violent protests in which rights groups say hundreds of people have been killed by security forces have flared up again in Ethiopia, with a US citizen among the latest deaths.

Protests reignited in the Oromia region – the main focus of a recent wave of demonstrations – after at least 55 people were killed in a stampede at the weekend, which was sparked by police firing tear gas and warning shots at a huge crowd of protesters attending a religious festival.

The official death toll given by the government is 55, though opposition activists and rights groups say they believe more than 100 people died as they fled security forces, falling into ditches that dotted the area. Ethiopian radio said excavators had to be used to remove some of the bodies.

Are Ethiopia’s Oromo being repressed?

The anti-government demonstrations started in November among the Oromo, Ethiopia’s biggest ethnic group, and later spread to the Amhara, the second most populous group. Though they initially began over land rights, they later broadened into calls for more political, economic and cultural rights.

Both groups say that a multi-ethnic ruling coalition and the security forces are dominated by the Tigray ethnic group, which makes up only about 6 percent of the population.

The government, though, blames rebel groups and foreign-based dissidents for stoking the violence.

Staff at the California-based UC Davis university confirmed the identity of the US citizen as Sharon Gray, a postdoctoral researcher of biology, who had been in the Horn of Africa nation to attend a meeting.

The US embassy said she was killed on Tuesday when stones were hurled at her vehicle on the outskirts of Addis Ababa, where residents said crowds have attacked other vehicles since the stampede.

The embassy did not give further details or a precise location for the incident.

Foreign firms attacked

News of Gray’s death came as foreign-owned factories and equipment were damaged in the protests. Demonstrators in Oromia say farmland has been seized to build foreign factories and housing blocks.

On Tuesday, crowds damaged a factory run by Turkish textile firm Saygin Dima and the Bmet Energy cable plant, which also has Turkish investors, officials from firms in the area said. Both plants are in the Oromia area.

READ MORE: The ‘Ethiopia rising’ narrative and the Oromo protests

A third of the Saygin Dima plant in Sebeta, 35km southwest of Addis Ababa, was destroyed by fire, Fatih Mehmet Yangin, general manager at the plant, said.

“A large crowd attacked the factory,” he said, adding three vehicles were destroyed.

Yangin said a flower farm nearby was also attacked. The Oromia Regional Administration said vehicles and some machinery at a plant owned by Nigeria’s Dangote Cement were vandalised.

Oromia has been a focus for industrial development that has fuelled Ethiopia’s economic growth, but locals say they receive little compensation when land is taken by the government.

The death toll from unrest and clashes between police and demonstrators over the past year or more runs into several hundred, according to opposition and rights group estimates. The US-based Human Rights Watch says at least 500 people have been killed by security forces.

The government says such figures are inflated.

The attacks will cast a shadow over Ethiopia’s ambition to draw in more investment to industrialise a nation where most people rely on subsistence farming, and have been struggling with a severe drought over the past two years.

The government has been building new infrastructure, including an electrified railway connecting the capital of the landlocked nation with a port in neighbouring Djibouti, which opened on Wednesday.

At least seven foreign-owned flower farms in Ethiopia’s Amhara region, another area where protests have flared up, were damaged in political violence at the start of September.

Bloggers arrested

Rights groups and opposition politicians accuse the government of excessive force in dealing with demonstrations, crushing opponents and stifling free speech.

WATCH: What is triggering Ethiopia’s unrest?

The Committee for the Protection of Journalists called on authorities on Tuesday to free Seyoum Teshoume , a blogger critical of the government, who writes for the website Ethiothinktank.com. The committee said he was reported detained on October 1.

Another blogger who has expressed support for the protests, Natnael Feleke, was arrested on Tuesday, according to a blogging collective of which he is a member. Natnael was previously arrested in 2014 and released after more than a year in prison when charges against him were dropped.

There were also reports that the internet had been shutdown periodically over the past two days.

Officials could not immediately be reached for comment, but the government says it only detains people who threaten national security and says it guarantees free speech.

The opposition failed to win a single seat in a 547-seat parliament in a 2015 election and had just one in the previous parliament.