Clashes between security forces and protesters erupt in Nepal's capital Kathmandu on Sunday.

The violence comes at the start of a three-day general strike over state boundaries that could push lawmakers past a May 27 deadline to write a new constitution.

At least two dozen vehicles were damaged by stone-throwing activists, and at least 46 people were detained.

A specially-elected assembly dominated by Maoists has missed several deadlines to prepare the majority-Hindu nation's first federal constitution.

Points of contention include the names, number and borders of the new states within the country.

Politicians have only one more week to finalise the long-overdue charter.

After that, the constitutional assembly assigned the task will be disbanded, which would plunge the country into political uncertainty.

It is unclear what exactly would happen if the deadline is missed, but some analysts say lawmakers could choose to extend the assembly in defiance of the Supreme Court.

Though unlikely, there is also a risk an early general election could be called.

Travis Brecher, Reuters