By Humeyra Pamuk and Simon Lewis

WASHINGTON (Reuters) -The State Department said on Thursday it was sending more consular officers to Kabul and other locations, including Qatar and Kuwait, to help with the evacuation effort from Afghanistan after the Taliban seized Kabul on Sunday.

State Department spokesman Ned Price said 6,000 fully processed people were currently at the airport in Kabul and would soon be boarding planes. He added Washington would nearly double the number of consular officers in Kabul, without disclosing how many are deployed.

A source said that White House officials told a congressional briefing on Thursday morning that the United States had evacuated 6,741 individuals, including 1,792 American citizens and legal permanent residents, from Kabul.

The source, who listened to the teleconference, quoted the briefers as saying that the "biggest bottleneck" was getting evacuees through crowds mobbing Kabul airport gates.

"The department is sending consular staffing teams to Qatar and Kuwait to assist with the transit effort and we're preparing teams to surge to other processing locations as well," Price said.

Once the consular capacity in Kabul is doubled, he said the State Department believes it will have the number of officers needed to process individuals and fill flights. The Pentagon has said its aim is to evacuate between 5,000 and 9,000 people a day.

The United States "significantly expanded" overnight the number of American citizens, locally employed staff, Special Immigrant Visa (SIV) applicants and other vulnerable Afghans eligible for departure, Price said, adding that about 20 flights would leave Kabul on Thursday night.

Thousands of people have desperately tried to get past Taliban roadblocks and U.S. troops to reach the airport. On Thursday, the Taliban urged crowds of Afghans waiting outside it to return home, saying they did not want to hurt anyone, a day after firing at protesters and killing three.

(Reporting by Humeyra Pamuk and Simon Lewis; Additional reporting by Jonathan Landay; Writing by Daphne Psaledakis; Editing by Peter Cooney)