India seamer Zaheer Khan claimed all nine Essex wickets to fall as the home side closed 186-9, 464 behind Worcs.

The visitors added 191 to finish with 650-7, Gareth Batty scoring only his second first-class century.

Varun Chopra and Mark Pettini shared 117 for Essex, but Zaheer came back with a stunning spell of swing.

Five balls after ousting Pettini he had Andy Flower caught at slip, then struck twice in his next over, before Andre Adams fell to the last ball of the day.

Zaheer will try to add last man Darren Gough to his collection when play resumes on Friday.

"I did start to think about taking all 10 wickets once the eighth wicket fell and it would be marvellous to achieve that, but the main thing is that Worcestershire are in a strong position," he said.