GUWAHATI, India, Jan 7 (Reuters) - Separatist rebels gunned down 10 people in two separate attacks in India's restive northeastern state of Assam on Sunday, police said. The killings raised the death toll in a wave of rebel violence since Friday night to 67. Police blamed the attack on the United Liberation Front of Asom (ULFA). Police said ULFA militants shot dead nine labourers at a brick kiln in the eastern district of Sivasagar and shot dead a businessman in the same district.