India's top court ordered authorities in northern Punjab state Thursday to share river water supplies with a neighbouring state, triggering a spate of resignations by angry lawmakers.

The water dispute between Punjab and Haryana has been simmering for over a decade, after a bilateral agreement to construct a 214-kilometre (133-mile) canal connecting two rivers in the states was unilaterally scrapped in 2004.

The Supreme Court said the Punjab government's decision to terminate the agreement via a state legislation was unconstitutional and defied the court's own earlier orders calling for the canal's completion.

"The State of Punjab had exceeded its legislative power in proceeding to nullify the decree of this Court and therefore, the Punjab Act cannot be said to be validly enacted," a five-judge bench headed by Justice A R Dave said in its order on Thursday.

Both the states depend on agriculture for employment and revenues, with farmers in Punjab saying they will suffer drought if the river water is diverted elsewhere.

The order was hailed as a "victory" by politicians in Haryana, which is ruled by an alliance led by Prime Minister Narendra Modi's Bharatiya Janata Party.

But in Punjab, dozens of legislators from the main opposition Congress party resigned from the state assembly in protest against the order.

Haryana's powerful caste councils have threated to launch an street agitation if Punjab fails to implement the order.

There are at least seven major water sharing disputes between 10 Indian states.

The disputes have often turned violent in recent years with protesters damaging a critical water supply canal to New Delhi in February.

Authorities in southern Karnataka state had to impose a curfew in Bangalore in September after riots erupted following a Supreme Court order to release millions of cusecs of water from the Cauvery river to neighbouring Tamil Nadu state.

Work on the disputed canal to connect Punjab's Sutlej river with the Yamuna in Haryana began in the 1970s, but a large section of it remains incomplete.