Supporters of defeated presidential candidate Mir-Hossein Moussavi have organized rallies across Iran to mourn those killed in recent post-election violence.

In Tehran, hundreds of thousands of protesters wearing black clothes started peaceful rallies from mosques across the Iranian capital and gathered in Imam Khomeini Square at 4 p.m. local time (1130 GMT).

Moussavi, a former prime minister, himself attended the rally. He briefly addressed the demonstrators, calling for calm and self-restraint.

Supporters in today's march are estimated to be as many as those in Monday's rally, which was the largest in a series of protests since the announcement of election results on Saturday.

Thursday's march marks the sixth day of rallies by Moussavi supporters in protest to the presidential election's results in which the former prime minister suffered a crushing defeat. Moussavi has rejected the final vote count as fraudulent.

Incumbent Mahmoud Ahmadinejad was re-elected on June 12 with almost two-thirds of votes, but Moussavi has demanded a re-run of the election.

Despite Moussavi's insistence on peaceful nature of protests, violence flared in early stages of demonstrations which started in the weekend. At least eight people were killed in Tehran and many others sustained injuries.

On Wednesday, crowds of supporters marched in silence from Haft-e Tir Square in central Tehran towards Vali Asr Square.

The protesters demand the Guardian Council, the body tasked with overseeing the presidential election process, nullify the election, asking for a re-run.

Top Reformist body, the Association of Combatant Clerics (Majma'-e Rowhaniyun-e Mobarez), has made a request to Tehran's governor's office to hold a pro-Mousavi rally on Saturday. Iranian authorities have banned the rallies as illegal.

The Guardian Council said Thursday that it would invite the June 12 presidential candidates to attend an upcoming meeting in which the body is to investigate complaints about the election.

According the council's spokesman, Abbas-Ali Kadkhodayi, 646 different counts of violation in the election have been filed by three candidates -- Mousavi, Mehdi Karroubi and Mohsen Rezaei.