Media playback is unsupported on your device Media caption Obama: We have to do everything we can

US President Barack Obama has announced fresh sanctions against Iran, Syria and those who help them use technology to perpetrate human rights abuses.

He announced the new sanctions against "digital guns for hire" in a speech at the US Holocaust Museum.

Mr Obama has also asked US intelligence groups to include assessments of the likelihood of mass killings in its co-ordinated reports.

He said: "National sovereignty is never a licence to slaughter your people."

The executive order creates sanctions against the government of Syria and Iran "and those who abet them, for using technologies to monitor, target and track its citizens for violence".

"These technologies should be in place to empower citizens, not to repress them," said Mr Obama.

On Monday, the US Treasury announced the specific targets of the sanctions, including Iran's Islamic Revolution Guard Corps, Syria's General Security Directorate and its chief Ali Mamluk, as well as the state-controlled mobile phone company, Syriatel.

Six of the seven targets were already subject to US sanctions, with the addition of Datak Telecom, an Iranian internet provider.

Mr Obama signed the executive order for the sanctions on Sunday.

Correspondents say that while mobile and social technology has been credited with helping bring about political and regime changes in other Middle East countries, some regimes have used technology to track dissidents or block internet access.

Iran has provided the government of Syrian President Bashar al-Assad with programs that jam mobile phones.

Social networking sites that the Syrian opposition would use to organise demonstrations have been blocked or monitored using similar technologies.

Before the speech, Mr Obama toured the museum for the first time as president, with writer and Holocaust survivor Elie Wiesel.

The US president lit a candle in the Buchenwald section of the museum's Hall of Remembrance. Mr Obama's great-uncle helped liberate the camp at the end of World War II.