(Reuters) - Two NATO soldiers were shot dead on Thursday by two Afghans, including a man believed to be an Afghan soldier, NATO said in a statement, an attack that is likely to raise further questions about the effectiveness of the country's security forces.

The killings, in the country's south, occurred after two senior U.S. officers were gunned down in the heart of Afghanistan's Interior Ministry on Saturday by what Afghan security officials say is a police intelligence official.

(Reporting by Michael Georgy, editing by Amie Ferris-Rotman)