KUALA LUMPUR (AFP) - Six Malaysian Muslims have reportedly been handed one-month jail terms for skipping prayers in violation of Islamic laws, sparking fresh concern on Wednesday (Dec 4) about rising religious conservatism in the multi-ethnic country.

Attending Friday prayers is obligatory for Muslim men in Malaysia, but it is rare for such harsh punishments to be meted out for missing them.

Aged 17 to 35, the men had been caught having a picnic by a waterfall instead of taking part in prayers on a Friday, the holiest day of the week for Muslims, newspaper Harian Metro reported.

They were also fined between RM2,400 (S$780) and RM2,500 each after pleading guilty on Sunday in a syariah court in the conservative north-eastern state of Terengganu.

They are still out on bail while they appeal against the sentences. They could have been jailed for a maximum of two years under Muslim-majority Malaysia's syariah laws.

"The alleged failure to attend Friday prayers is a personal matter," Zaid Malek, from rights group Lawyers for Liberty, said in a statement.

"While such acts may be considered improper by some in Muslim society, criminal punishment is excessive and not the way to address them." He also said the sentences ran counter to pledges from the religious affairs minister to focus on rehabilitation of criminals, rather than punishment.

Critics said the case highlighted that a traditionally tolerant brand of Islam in Malaysia was being eroded, and it came weeks after four men were caned for having gay sex in violation of syariah laws.

Malaysia has a dual-track legal system, with syariah courts handling some cases for Muslim citizens.

Some 60 per cent of Malaysia's 32 million people are ethnic Malay Muslims and the country is also home to substantial ethnic Indian and Chinese communities, who do not usually follow Islam.