A grand jury in Washington has indicted three more Turkish security guards for attacking protesters in May during a visit by Turkish President Recep Tayyip Erdogan to the US capital.

Tuesday's indictment brings to 19 the total number of people charged with attacking peaceful protesters and police officers on May 16, shortly after Erdogan met with President Donald Trump at the White House. Fifteen of the 19 are Turkish security guards. 

Read more: US politicians want apology for Erdogan bodyguards attack

Guards attacked Kurdish, Armenian protesters

Eleven people were injured in the melee outside the Turkish ambassador's residence.

Video from the incident shows Erdogan supporters and his guards attacking Kurdish and Armenian protesters.

US officials strongly condemned the attack at the time. Turkey has said the security guards have diplomatic immunity.

Turkey has defended the guards' actions, saying they intervened because police failed to stop protesters linked to the Kurdistan Workers' Party (PKK) from being so close to Erdogan.

The PKK is considered a terrorist group by Turkey and the United States.

Relations between Ankara and Washington are strained over Washington's support of Syrian Kurdish forces battling the so-called "Islamic State." Turkey says the US-backed Syrian Kurds are an arm of the PKK.

Maximum of 15 years in prison

Sixteen of the defendants were charged in June.  

Two people were arrested in June and face a court hearing in September. The rest returned to Turkey and are unlikely to face a court. However, they could be arrested if they return to the United States. The felony charges carry a maximum of 15 years in prison.

During a March 2016 visit by Erdogan in Washington, his guards also scuffled with protesters and journalists outside a think tank event. 

cw/cmk (AFP, AP, Reuters)