"The US Embassy in Kabul warns US citizens that extremist organizations continue to plan attacks against a variety of targets in Afghanistan, including a heightened risk of attacks targeting female government and civilian workers, including teachers, human rights activists, office workers, and government employees," the diplomatic mission said in a statement.

At the same time, it did not specify which organizations could carry out the attacks.

The intra-Afghan peace talks started in Doha on Saturday after the Afghan government and the Taliban movement successfully completed a long-awaited prisoner exchange arrangement.

The talks are now expected to pave the way for a peace process and withdrawal of foreign troops from Afghanistan after almost two decades of war and insurgency.