Two people whom the Ugandan army describe as "armed terrorists" have been killed in the capital, Kampala, as the country marks Martyrs Day - a Christian celebration to commemorate the faithful who died in the 19th Century.

A counter-terrorism unit "intercepted and neutralised" the two, one of whom was a female suicide bomber, in the upmarket suburb of Munyonyo, army spokesperson Chris Magezi said.

The incident took place near the Roman Catholic Munyonyo Martyrs' Shrine, where a group had gathered to pray, local media reported.

Reports also cited an explosion, with an eyewitness telling Uganda's Daily Monitor newspaper that the blast occurred as the two approached the church on a motorcycle.

There were no other casualties, the Reuters news agency reports.

The army spokesperson did not confirm the blast, but added that the authorities were on "heightened alert".

One of those killed was a female "suicide bomber laden with powerful explosives", Col Magezi said in a post on X.

Footage from Uganda's NBS Television showed security and forensics personnel at the scene of the incident, after having sealed off the area.

Col Magezi told Reuters that it was believed the two people were linked to the Allied Democratic Forces (ADF), which is an affiliate of the Islamic State (IS) group.

The ADF has not yet commented.

Uganda has historically faced threats from the group.

Last year, the army warned citizens that the ADF was planning to attack places of worship, public events, schools and urban areas.

A year earlier, in 2023, the group was accused of carrying out a fatal attack on a Ugandan school which led to the killing of nearly 40 students.

The Martyrs Day event, one of the largest Christian pilgrimages in Africa, draws millions of believers each year to honour 45 people, made up of 22 Catholics and 23 Anglicans, who were killed between 1885 and 1887 on the orders of Kabaka Mwanga II of Buganda for refusing to renounce their faith.

The monarch demanded they revert back to their traditional religion, but they refused and were accused of disobeying him and later burned to death for it.