"Hitherto, photographers have had no problems in entering hospitals to report on the casualties of war," the FMM said.
"It is highly likely that these measures have been taken after heavy losses (numbering in the hundreds) faced by the Sri Lankan army earlier this week after fighting intensified in the north."
In a sign of the ongoing confusion over casualty figures, the government-controlled Daily News reported that 200 fighters from the Liberation Tigers of Tamil Eelam (LTTE) had been killed in the battle.
But official defence ministry figures cited only 43 soldiers dead and 38 missing from Wednesday's fighting in the northern peninsula of Jaffna.
"Some of the senior officers have been told that the army lost 185, including 20 who are still listed as missing," AFP reported a military source as saying.
"We are trying to establish the fate of the missing."
On Thursday, the government reported killing more than 100 Tamil fighters and wounding 100 more in the pre-dawn offensive along the Muhamalai front lines on the peninsula.
But the Tigers said only 25 of its fighters were killed.
Official defence ministry casualty reports and LTTE figures can seldom be verified because the government prevents journalists from visiting war zones and territory held by the Tamil Tigers.
Both sides are also thought to underplay their own losses while overstating those of their opponents.
The ministry claims 3,105 Tamil Tigers have been killed already this year, more than the total number of fighters as estimated by intelligence sources - which say the LTTE has only 3,000 fighters in total.
The increased casualty figures make Wednesday's confrontation by far the biggest battle since Colombo withdrew from a Norwegian-arranged truce in January.
Despite the heavy losses in Jaffna, Sri Lankan forces on Friday took control of a Roman Catholic church that religious groups had feared was in danger of being damaged by by civil war.
But while the government seized the church in Madhu - which had been abandoned by the Tamil Tigers - a statue of the Virgin Mary, which is a magnet for mass pilgrimages, remained in LTTE-controlled territory.
The church, in the coastal Mannar district, has in the past provided a sanctuary for thousands of civilians sheltering from the crossfire, the ministry said.
It accused the LTTE of turning the shrine into "a terror base by positioning its heavy guns around the church and using it as a barrack" since they took control of the area in 1999.