The US Treasury imposed sanctions on Gertler in 2017 and 2018, accusing him of leveraging his friendship with former Congo President Joseph Kabila to secure lucrative mining deals.
The assailants fired guns at people working in fields in Mulekera commune outside Beni, Mulekera Mayor Ngongo Mayanga said on Saturday.
A UN source said they were investigating "credible" allegations of over fifty deaths after soldiers blocked the protesters.
To date, only five countries have opened Jerusalem embassies: the United States, Honduras, Guatemala, Kosovo and Papa New Guinea.
In the Ituri province, some 3 million people are in desperate need of aid, according to a UN humanitarian agency.
Uganda's military has vowed to keep hunting terrorists but stated that ADF fighters who surrender will be given amnesty.
The president of Uganda has accused a former leader from the Democratic Republic of Congo of providing sanctuary and resources to Islamist rebels.
"At least 20 suspected ADF collaborators have been arrested, to assist with our investigations," the country's police force said in a statement.
The bill has been criticized by human rights organizations, who are calling it unconstitutional, fearing that it could reignite violence in the recently war-torn state.