Two Angolans, sports journalist Amor Carlos Tomé and political activist Francisco Oliveira, were tried on similar charges of participating in a Russian-linked influence operation, which both denied.
Tomé was sentenced to two years probation and Oliveira was acquitted.
The prosecution appealed immediately after the ruling was read after 23:00 local time on Tuesday.
Tomé is expected to remain in custody pending the outcome of his appeal.
The BBC contacted the Russian Embassy in Angola for comment but had not received a response at the time of going to press.
Ratchin and Lakshtanov’s lawyer, Elizeu Nguiniti, told the BBC he would not comment on the decision.
After the verdict was read, he told the court he disagreed with the decision, which found his client guilty on four of 11 charges – criminal involvement, espionage, terrorism and possessing illegal currency – but said he accepted the court’s decision.
The Russians told the court at a previous hearing that they had held closed-door meetings with politicians from the ruling MPLA and the opposition Unita party, but denied the meetings were linked to illegal activities, according to Novo Jornal, a privately owned Angolan news site.
The court reportedly denied the defense’s request to call several of these politicians as witnesses, ruling that their testimony was “not necessary” to establish the facts of the case.
Prosecutors alleged the defendants played a role in organizing deadly unrest in Angola in 2025.
They claimed the Russians paid more than $24,000 (£18,000) to local journalists and pundits to spread pro-Russian and anti-government content intended to stimulate political change in Angola.
They also cited publications related to the operation found on the defendants’ devices, notes and photos related to the 2025 protests, as well as alleged contacts with senior Angolan politicians.
Many Angolan activists strongly disagree with prosecutors’ claims that the protests did not arise organically.
Novo Jornal previously reported that Lakshtanov told the court during one of the hearings that he had lived and worked in Angola for almost 40 years and that his long academic career was incompatible with his involvement in a terrorist organization.
Ratchin previously explained to the court that he was a businessman who came to Angola to set up a Russian cultural center and that the payments he made to various individuals were compensation for services rendered, Novo Jornal reported.
He said he was surprised by the charges that followed his arrest in August 2025.
The initial proceedings of the trial, which began last March, were marred by controversy.
During the first hearing, prosecutors refused to read the indictment aloud in court. She argued that a formal reading was not necessary because the defendants already knew of the accusations against them.
The defense counsel disagreed. They argued that because the trial is public, people attending the trial, including journalists, should be able to hear and understand the charges.
Nevertheless, the prosecution refused to read the indictment, saying it was optional.
The indictment itself was criticized even before the trial began.
Since then, the defense team has continued to challenge its contents, arguing that it often relies on assumptions rather than concrete evidence.
The BBC had previously identified a number of typographical errors and obvious factual errors in the document, but had not received a clear explanation from prosecutors.
Additional reporting by Ilya Barabanov and the BBC Russian investigative team
