Russian Foreign Minister Sergei Lavrov said on Monday that the two female suicide bombers in the twin subway explosions may have links to militants on the Afghan-Pakistani border, Interfax news agency said.

Asked if any foreign elements were involved in the terrorist attacks, which killed at least 38 people and injured 64 Monday morning, Lavrov said he did not exclude that.

"We all know that the Afghan-Pakistani border, in the so-called no-man's land, the terrorist underground is very well entrenched," he said.

"We know that many people there actively plot attacks, not just in Afghanistan, but also in other countries. Sometimes the trails lead to the Caucasus," he added.

Meanwhile, Russia's FSB state security service said the two suicide bombers may have links to the North Caucasus, the center of an insurgency movement against Moscow.