Sri Lanka will dispatch a high-level delegation to Russia to investigate the fate of hundreds of nationals reportedly fighting in the war in Ukraine, a top official said on Thursday.

Social media campaigns via WhatsApp have targeted ex-military personnel with promises of lucrative salaries and promises of citizenship, the Defence Ministry has said, warning its nationals not to be duped.

The messages, sent by Sri Lankan nationals, provide a number to agents, who then arrange the documentation and the flights.

The campaigns have proved appealing as Sri Lanka struggles to emerge from its worst financial crisis in more than seven decades, which has doubled poverty rates from pre-pandemic levels and pushed hundreds of people to migrate.

Earlier this month, Sri Lankan authorities launched investigations into reports of its citizens, mostly with military training, being trafficked to fight in the war in Ukraine, said State Minister for Foreign Affairs Tharaka Balasuriya.

"The primary challenge lies in determining the exact number of individuals in Russia. As per unofficial sources, approximately 600-800 Sri Lankan individuals are in Russia," he told reporters.

Russia's embassy in Colombo did not immediately reply to a request for comment and in the past Moscow has not responded to repeated requests from Reuters on this issue.

Sri Lanka's authorities have received 288 complaints from family members of nationals who had left illegally to fight in Ukraine and have arrested seven people, including a retired major general, linked to the human trafficking, according to the island nation's defence ministry.

At least 16 retired military personnel have died in Ukraine, the ministry said.

Sri Lanka's Defence Secretary Kamal Gunaratne, and a former ambassador to Russia will be among the delegates who will leave for Russia shortly, Balasuriya said.

In 2009, Sri Lanka ended a 26-year civil war between separatist Tamil insurgents and government forces. After the conflict many Sri Lankan military personnel retired from active service.

(Reporting by Uditha Jayasinghe; Editing by Sharon Singleton)