A six-month ceasefire by one of Iraq's most powerful groupings may not be renewed, an aide to influential Shi'ite cleric Moqtada al-Sadr's warned today.
And later, seven people returning from a Shi'ite religious event were killed in a rocket attack in the northwest of Iraq.
Another eight people were wounded when a Katyusha rocket hit a group of people who had been observing the Ashura religious ritual in Tal Afar, said police Brigadier General Najim Abdullah.
One of the key reasons for a decline in Iraqi violence in recent months has been the cessation of operations by al-Sadr's Mehdi Army.
But operations to root out militants have been condemned by Salah al-Ubaidi, a senior official in Sadr's political movement in the holy Shi'ite city of Najaf.
He accused "criminal elements" within Iraq's security forces of attacking al-Sadr's followers and Mehdi Army fighters.
"If the government security forces do not stop their campaigns of detention and arresting our followers, we may reconsider our decision to freeze the Mehdi Army," Ubaidi said.
The six months of the declared ceasefire run out next month.
Al-Sadr announced the cessation of hostilities after clashes between his followers and police during a pilgrimage in Kerbala, another holy Shi'ite city, last August.
The fighting, in which scores were killed and hundreds were wounded, sparked outrage and prompted a police investigation.
Police this month freed 51 al-Sadr followers held since the violence. Mr Ubaidi, however, said thousands were still being held.
"The government must release all of our people who were arrested, especially after the events of Kerbala last year," Mr Ubaidi said.
Al-Sadr draws support from poor, urban Shi'ites and led two uprisings against US forces in 2004. His followers have been locked in a battle for control of southern Iraq and its oil wealth with followers of his main Shi'ite rival, the Supreme Islamic Iraqi Council (SIIC), headed by Abdul Aziz al-Hakim.
Sadrists accuse SIIC followers of infiltrating the security forces and attacking them. Violence across Iraq has fallen 60 per cent since June, and US military commanders say the Mehdi Army ceasefire has been crucial to the improvement in security.