WASHINGTON — President Obama warned Syria’s government Monday that it would be ‘‘totally unacceptable’’ to use chemical weapons against its own people and vowed to hold accountable anyone who did, as US intelligence officials picked up signs that such arms might be deployed in the ongoing insurgency.

The White House said that some recent actions by the government of President Bashar Assad were indicators that Syrian forces were preparing to use such weapons, following earlier reports that intelligence agencies had noticed signs of activity at chemical weapons sites. Obama’s spokesman said the administration had ‘‘an increased concern’’ of possible use of chemical weapons.