Nigerian workers from an oil labor union have extended a strike to oil majors Chevron Corp. (NYSE: CVX), Shell (NYSE: RDS.A) and Eni subsidiary Agip in protest over the sacking of members from ExxonMobil Corp. (NYSE: XOM), the union’s general secretary said on May 16.

Nigerian labor unions have held a number of strikes in the last few months in protest at the sacking of workers by oil companies. Members of the Petroleum and Natural Gas Senior Staff Association of Nigeria (PENGASSAN) began a strike at ExxonMobil last week.

PENGASSAN General Secretary Lumumba Okugbara said the union’s 10,000 members were taking part in the three-day nationwide strike, which began on May 16 and would continue until May 17.

“Production activities are still on and our members on essential duties are working. Only those in administrative duties are not working in the various multinational oil companies since yesterday,” he said.

The strikes are in protest at the sacking of 150 workers in December, of which 82 were PENGASSAN members. Okugbara said union representatives would meet ExxonMobil management on May 16 for talks.

Strikes by ExxonMobil workers in Nigeria at the end of 2016 did impact output, leading to weekslong loading delays.