The Somali militant Islamist group al-Shabab has made another threat to target buildings in Nairobi, Kenya, following a bomb attack Monday in the city's downtown.

According to IntelCenter, a private intelligence firm based in Alexandria, Virginia, al-Shabab posted threats online Wednesday, saying that something big is coming within the next two weeks and that Kenya would soon watch its towers coming down, the Associated Press reported.

Two weeks from now you will weep, the post read.

This is the third instance in which the terrorist group has threatened to attack Kenya's capital in the past year. The first came last October, after Kenyan troops were deployed to neighboring Somalia to fight al-Shabab militants.

Following al-Shabab's proclamation, Nairobi was hit by a series of grenade attacks, killing at least 40 people. The Kenyan government blamed al-Shabab for the attacks.

A second threat was made in January, and earlier this week an IED was detonated in downtown Nairobi, ripping open an office building, killing one person and wounding dozens more.

Al-Shabab has not claimed responsibility for the recent attack, but Kenyan authorities suspect the group was behind it.

IntelCenter said the threat of a large-scale terrorist attack against Kenya is very high within the next few months, given the increasing number of threats and small-scale attacks linked to al-Shabab.

The towers most likely to be targeted are those housing hotels, especially those frequented by Westerners, government offices, media and prominent corporations. The building volume of threats and low-level activity indicate that such an attack may be attempted sooner rather than later, IntelCenter said, AP reported.

Al-Shabab (Youth in Arabic) controls southern and central regions of Somalia, and has ties to the higher-profile terrorist organization, Al-Qaida, which has provided fighters, seasoned by the conflicts in Iraq and Afghanistan, to the group.