(CNN) -- Syria's President Bashar al-Assad "must step aside," European Union foreign ministers said in a blistering statement Monday, adding the Syrian government's crackdown on anti-government protesters may amount to crimes against humanity.
The EU also expanded sanctions on Iran and Belarus to protest their crackdowns on their citizens, it announced.
But the 27 foreign ministers of the union reserved their sharpest criticism for Syria and its president.
"The EU condemns in the strongest possible terms the ongoing brutal repression led by the Syrian regime," they said after a meeting in Luxembourg.
Syria's leader must resign "to allow a political transition to take place in Syria," they said.
And they welcomed the creation of the umbrella opposition Syrian National Council, a day after Syria's foreign minister warned other nations against recognizing it.
The ministers said they were "deeply disappointed" that the United Nations Security Council failed to increase sanctions on Syria -- a milder statement than had been expected.
EU foreign policy chief Catherine Ashton said the union would continue to press for strong action on Syria.
The harsh words on Syria follow last week's failure by the U.N. Security Council to agree on a resolution calling for an immediate end to a military crackdown against opponents of President al-Assad.
China and Russia opposed the resolution, which was supported by the EU's Great Britain and France as well as the United States.
Al-Assad has been under international pressure to end a seven-month crackdown on demonstrators calling for the end to his regime.
The European Union has slapped Syria with a number of sanctions, including barring the import of Syrian oil and banning the delivery of Syrian currency produced in the EU to the Syrian Central Bank. It also has placed travel restrictions on and frozen the assets of officials it says are involved in the attacks on the opposition.
The European Union is also expanding its sanctions on Iran in light of "growing concern about the human rights situation" there, Ashton announced Monday.
She expressed concern about "repression of citizens and human rights defenders, journalists, women activists, minority groups, members of the opposition."
She called on Iran to "fully respect the rights of their people."
Iran was already under EU economic and trade sanctions related to its nuclear program.
Ashton said the union was continuing to talk to Tehran about its controversial nuclear ambitions.
The EU also renewed and expanded sanctions on Belarus.
Nearly 200 people were already subject to an asset freeze and travel ban over the "crackdown on civil society and democratic opposition" after the last two presidential elections.
The EU added three companies and 16 individuals to the list of those facing restrictions, and it extended the existing restrictions until the end of October 2012, it announced. It is expected to name them on Tuesday.
The ministers extended the visa ban and asset freeze on 192 people in Belarus who the EU maintains are responsible for political repression and "violations of the international electoral standards" in the former Soviet republic's 2006 and 2010 presidential elections.
The sanctions were imposed against Belarus following the December 2010 presidential election that saw the re-election of President Alexander Lukashenko amid allegations of widespread electoral fraud.
The government cracked down on mass protests following the election, including the beating and jailing of former presidential candidate Uladzimir Nyaklyaeu. Other political figures and journalists also were jailed.
The ministers also expressed support for Libya's interim government.
Ashton said the existing EU office in Tripoli would soon become "a fully-fledged EU delegation."
CNN's Chelsea J. Carter contributed to this report.