The Taliban seized two key cities in Afghanistan Friday, as major hubs across the country have fallen and the United States moved fast to evacuate its citizens.

The capture of Herat and Kandahar marks the biggest achievements yet for the militant group, who have occupied 12 of the country's 34 provincial capitals as part of a week-long assault, the Associated Press reported.

The Taliban's rapid occupation capped three weeks of intense clashes in which both men and women were forced to use weapons to defend their city while many locals fled gunfights and mortar attacks.

Afghan officials have now lost their grip on most nations after a seven-day onslaught into urban centers by the Taliban has left the government and its U.S. backers dumbfounded.

The U.S. said Thursday it would send in 3,000 soldiers to help secure the pullout of American personnel from its consulate in Kabul.

U.S. State Department representative Ned Price said the move is not an "abandonment" or "wholesale withdrawal," NBC News reported.

Separately, the United Kingdom said around 600 military personnel would be mobilized to support British nationals leaving Afghanistan. Canada said it would also deploy special forces to help evacuate its embassy.

According to a report by BBC News, a leaked U.S. intelligence report estimated that the Taliban would attack Kabul within weeks, and the Afghan government could collapse within three months.

Experts said it is difficult to measure the Taliban's actual strength. The U.S. Combating Terrorism Center at West Point (USCTC) estimates suggest a core fighting capability of 60,000 armed fighters.

That figure could top 200,000, with the inclusion of other militia organizations. In comparison, Afghan special forces are small in number, about 10,000 strong, and they are already heavily depleted.

On Thursday, Taliban fighters captured police detachments and government offices in Herat and massed up on the streets, firing their weapons in jubilation of its major military takeover.

The Taliban are also fast approaching Logar province, just south of the country's capital city. The Afghan government may have no choice but to withdraw to defend Kabul and a few other cities in the next few days if the Taliban continue to advance.